Patent Publication Number: US-7896827-B2

Title: Knee brace and method for securing the same

Description:
This application claims the benefit of U.S. Provisional Application Nos. 60/637,754 filed 22 Dec. 2004, 60/684,163 filed 25 May 2005, and 60/739,407 filed 25 Nov. 2005. 
    
    
     BACKGROUND 
     A. Background Information on Knee Braces 
     Knee braces are widely used to treat a variety of knee infirmities. Such braces may be configured to impart forces or leverage on the limbs surrounding the knee joint in order to relieve compressive forces within a portion of the knee joint, or to reduce the load on that portion of the knee. Moreover, in the event that knee ligaments are weak and infirm, a knee brace may stabilize, protect, support, or rehabilitate the knee. 
     The knee is acknowledged as one of the weakest joints in the body, and serves as the articulating joint between the thigh and calf muscle groups. The knee is held together primarily by small but powerful ligaments. Knee instability arising out of cartilage damage, ligament strain and other causes is relatively commonplace since the knee joint is subjected to significant loads during the course of almost any kind of physical activity requiring the use of the legs. 
     A healthy knee has an even distribution of pressure in both the medial and lateral compartments of the knee. It is normal for a person with a healthy knee to place a varus moment on the knee when standing so that the pressure between the medial and lateral compartments is uneven but still natural. 
     One type of knee infirmity that many individuals are prone to having is compartmental osteoarthritis. Compartmental osteoarthritis may arise when there is a persistent uneven distribution of pressure in one of the medial and lateral compartments of the knee. Compartmental osteoarthritis can be caused by injury, obesity, misalignment of the knee, or simply due to aging of the knee. 
     A major problem resulting from osteoarthritis of the knee is that the smooth cartilage lining the inside of the knee wears away. This leads to a narrowing of the joint space with the development of cysts and erosions in the bone ends. Because of the narrowing of the joint, bone comes directly in contact with bone, and an uneven distribution of pressure develops across the knee which may result in the formation of bone spurs around the joint. All of these changes ultimately lead to increasing pain and stiffness of the joint. 
     While there are no cures to osteoarthritis, there are many treatments. Individuals who have a diagnosis of isolated medial compartmental osteoarthritis of the knee are confronted with a variety of treatment options such as medications, surgery, and nonsurgical interventions. Nonsurgical interventions include the use of canes, lateral shoe wedges, and knee bracing. 
     Knee bracing is useful to provide compartment pain relief by reducing the load on the compartment through the application of an opposing external valgus or varus moment about the knee joint. Unloading knee braces have been shown to significantly reduce osteoarthritis knee pain while improving knee function. 
     B. Prior Art Knee Braces 
     There are many known unloading knee braces. An example of a known brace is described in U.S. Pat. No. 5,277,698 assigned to Generation II Orthotics, Inc. of British Columbia, which is incorporated herein by reference. Typically, braces of this type are designed to apply a moment about the knee through two mechanisms. The first mechanism is through the angulations of hinge components which induce a bending moment at a hinge. The second mechanism is provided by a three-point bending system via a force strap that spirals around the knee and applies a force to a prescribed aspect of the knee. 
       FIGS. 1 and 2  exemplify the application of forces by the brace on a leg and over a knee joint according to U.S. Pat. No. 5,277,698. The arrows B 1  and B 2  show lateral and force strap forces. The resulting moments in the leg due to lateral forces are shown by arrows Y 1  and Y 2 . The principal force A is that applied immediately adjacent that compartment of the knee having osteoarthritis.  FIG. 2  shows R as the normal axis of rotation of the knee. The resultant moment Y R  is a single rotational moment. 
     It has been found that as the force strap is increased in tension, the hinge valgus producing moment decreases. Therefore, the force strap and the hinge are found not to be adequately working in harmony. More specifically, it was discovered that the hinge produces about 20% of the total valgus moment in this brace. It is believed that since the hinge is aligned close to the knee, the strap urges the knee against the hinge. Moreover, the rigidity of this type of hinge limits the displacement of the hinge relative to the knee. 
     In a conventional brace having a hinge, a clearance is provided between the hinge and the knee to allow for movement of the knee towards the hinge. This results in a bulky brace since a large hinge is required which may extend at least an inch away from the knee. 
     It has been determined that if more unloading of the knee is required by the brace than is obtained from normal strap tension, and if the force strap is further tightened, the knee is drawn towards the hinge and might strike the hinge. This results in the hinge applying forces to the knee that counteract the force applied by the force strap. In turn, the additional tightening of the force strap is mitigated or negated by the force exerted onto the knee from the hinge. 
     For example, a study was conducted on a patient wearing a conventional knee brace having a force strap. In normal strap tension, the force strap component unloaded 5.8 Nm of the knee and the hinge unloaded about 2.2 Nm. By increasing the force strap tension, the unloading of the force strap resulted in 11.6 Nm, but the hinge resulted in unloading −2.4 Nm since the hinge was pressed against the knee. 
     As will be more fully evident in the ensuing discussion, the embodiments described herein are provided to overcome the deficiencies of prior art unloading braces by including arrangements that provide maximum unloading of the knee brace, while removing the mitigating effects of the hinges in known knee braces. Moreover, the embodiments of the invention are arranged for treating compartmental osteoarthritis, and have improved mechanical properties that remove undesirable rotational forces incurred by the brace and provide a more effective mechanism for generating a valgus or varus moment at the knee. 
     While known knee braces are successful at reducing pain at or stabilizing a knee joint, many users find these braces to be bulky, difficult to don, complicated to configure, and uncomfortable to wear. For these reasons, the embodiments described herein have streamlined features capable of providing relief for medial or lateral compartmental osteoarthritis, or functional stability of the knee without the attendant drawbacks of known unloading knee braces. 
     SUMMARY 
     Embodiments of the present invention are directed to an improved knee brace and knee bracing method that serve to reduce the effects of either medial compartmental or lateral compartmental osteoarthritis. Embodiments of the knee brace and variations of the knee bracing method reduce the effects of compartmental osteoarthritis by applying multiple forces to the knee on the side remote from the compartment having osteoarthritis while providing forces on the side of the compartment to maintain the brace securely on a leg while minimizing rotational forces. 
     According to one embodiment of the knee brace, proximal and distal breathable shells are inserted into pockets defined by a sleeve and spacer-elements corresponding to the shells. First and second force straps are connected to the shells and intersect at an intersection point located between the first and second shells, and posterior the normal axis of the knee brace. A tightening device is provided for each force strap to tension or release tension of the force straps against a leg of a user of the knee brace. 
     In another embodiment of the knee brace, a proximal frame member and a distal frame member each have inner and outer facing surfaces. A connecting element links the frame members. At least one force strap is connected to the frame members. The at least one force strap has first and second portions that intersect at an intersection point between the proximal and distal frame members. 
     In a variation of these embodiments, the at least one force strap is defined as a single substantially inelastic strap that is connected to and spirals between the frame members. The strap defines a first portion having a first end anchored to the proximal member and a remainder of the first portion connecting to the distal member. A second portion of the strap is connected to the distal member and a second end thereof secures to the proximal member. The first and second strap portions intersect at an intersection point between the proximal and distal members that is preferably located posterior the normal axis of the knee brace. 
     According to yet another embodiment, the knee brace is provided with at least one breathable spacer element having an inner surface connected to an inner facing surface of at least one of the proximal and distal members. The at least one spacer element defines an outer surface opposing the inner surface and includes a frictional feature. 
     In one variation of this spacer element, both the spacer element and the frictional feature are perforated. According to this variation the spacer element is a textile having a surface with a plurality of apertures upon which a silicone is coated along the non-apertured portions thereof. This yields a highly breathable spacer element that provides resistance to rotational forces caused by the force straps. Moreover, a spacer element on both proximal and distal portions of the knee brace prevents the proximal and distal portions of the knee brace from drawing closer to one another due to the forces applied by the force straps. 
     In combination with the force straps and spacer elements, one can achieve more unloading forces than with one force strap without increasing the pressure applied to the knee. This is due to the total unloading moment that is doubled with two force straps; the same amount of pressure is applied to the knee since there are two pressure points. 
     Second proximal and distal principal points of force are generated by the spacer elements secured to the frame members on a second side of the leg at locations above and below, respectively, the first proximal and distal principal points of force. The spacer elements maintain the knee brace on a leg and the frame members apart. The spacer elements may remove the need for a hinge as is used in the prior art braces. 
     Multiple other embodiments of a knee brace and variations of components thereof are discussed more fully in the discussion that follows. The features of the various embodiments of the knee brace result in a knee brace that provides not only greater unloading of the knee, but also result in a knee brace that is simpler to use and has a slimmer profile than conventional knee braces. 
     Of course, other methods, embodiments, and variations thereof are described in greater detail in the following discussion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
         FIG. 1  is a schematic view of forces applied on a leg using a prior art knee brace; 
         FIG. 2  illustrates the rotational force applied on a leg by the prior art knee brace of  FIG. 1 ; 
         FIG. 3  is a perspective view of an embodiment of a knee brace divided along anterior-posterior, proximal-distal, and lateral-medial planes; 
         FIG. 4  is a front elevation view of the embodiment of  FIG. 3  divided along the lateral-medial and proximal-distal planes; 
         FIG. 5  is a side elevation view of the embodiment of  FIG. 3  divided along the anterior-posterior and proximal-distal planes; 
         FIG. 6  is a top plan view of the embodiment of  FIG. 3 , divided along the anterior-posterior and lateral-medial planes; 
         FIG. 7  is a perspective view of an embodiment of a knee brace of the invention; 
         FIG. 8  is a front elevation view of the embodiment of  FIG. 7 ; 
         FIG. 9  is a medial side elevation view of the embodiment of  FIG. 7 ; 
         FIG. 10  is a lateral side elevation view of the embodiment of  FIG. 7 ; 
         FIG. 11  is an exploded view of the embodiment of  FIG. 7  without a sleeve; 
         FIG. 12  is a schematic view of forces applied on a leg using the brace shown in  FIG. 7 ; 
         FIG. 13  illustrates the rotational force applied on a leg by the brace of  FIG. 7 ; 
         FIG. 14  generally illustrates where the force is applied externally of the knee in the brace of  FIG. 7 ; 
         FIG. 15  is a sectional view taken along line XV-XV of  FIG. 14 ; 
         FIGS. 16 and 17  are perspective views of a variation of the force strap and the stability strap, respectively; 
         FIG. 18  is a detailed perspective view of the proximal shell of  FIG. 11 ; 
         FIG. 19  is a detailed perspective view of the distal shell of  FIG. 11 ; 
         FIG. 20  is a detailed sectional view of cut-away XX-XX in  FIG. 11 ; 
         FIG. 21  is a detailed section view of  FIG. 20  generally rotated about 180°; 
         FIG. 22  is a front elevational view of another variation of a proximal shell; 
         FIG. 23  is a front elevational view of another variation of a distal shell; 
         FIGS. 24-27  are force diagrams showing pressure distribution across prior art frame members and the proximal shell of the brace in  FIG. 7 ; 
         FIG. 28  is a frontal perspective view of the sleeve of  FIG. 7 ; 
         FIG. 29  is a rear perspective view of the sleeve of  FIG. 7 ; 
         FIG. 30  is a front elevational view of a sleeve embodiment for the knee brace; 
         FIG. 31  is a perspective view of a feature of the sleeve of  FIG. 30 ; 
         FIG. 32  is a sectional view taken along line XXXII-XXXII of  FIG. 11 . 
         FIG. 33  is a perspective view of a variation of a tightening device on an embodiment of the knee brace; 
         FIG. 34  is a plan view of the tightening device according to  FIG. 33 ; 
         FIG. 35  is a schematic plan view of the tightening device according to  FIG. 33 ; 
         FIG. 36  is a perspective view of another variation of a tightening device on an embodiment of the knee brace; 
         FIG. 37  is a perspective view of yet another variation of a tightening device; 
         FIG. 38  is an elevational view of the tightening device of  FIG. 37 ; 
         FIG. 39  is a rear elevational view of the tightening device of  FIG. 37 ; 
         FIG. 40  is a front elevational view of the tightening device of  FIG. 37 ; 
         FIG. 41  is a perspective view of a variation of the base of the tightening device of  FIG. 37 ; 
         FIG. 42  is a top plan view of the base in  FIG. 41 ; 
         FIG. 43  is an elevational view of the base in  FIG. 41 ; 
         FIG. 44  is perspective view of another variation of a tightening device including the base in  FIG. 41 ; 
         FIG. 45  is a perspective view of the tightening device according to  FIG. 44  secured onto the shell of  FIG. 22 ; 
         FIG. 46  is a elevational view of another variation of a tightening device; 
         FIG. 47  is a top plan view of the tightening device according to  FIG. 46 ; 
         FIG. 48  is a bottom plan view of the tightening device according to  FIG. 46 ; 
         FIG. 49  is a perspective view of yet another variation of a tightening device in an embodiment of the knee brace; 
         FIGS. 50-52  show an embodiment of a strap attachment piece; 
         FIGS. 53-55  are perspective views of a variation of a buckle assembly of the knee brace; 
         FIG. 56  is top plan view of another variation of a buckle assembly; 
         FIG. 57  is a bottom plan view of  FIG. 56 ; 
         FIG. 58  is perspective view of the buckle assembly of  FIG. 56 ; 
         FIG. 59  is a perspective view of another variation of a buckle assembly; 
         FIG. 60  is a schematic perspective view of another embodiment of the knee brace; 
         FIG. 61  is an elevational view of a variation of a hinge for the knee brace; 
         FIG. 62  is an elevational view of another variation of a hinge; 
         FIG. 63  is a perspective view of another embodiment of the knee brace; and 
         FIG. 64  is a perspective view of another embodiment of the knee brace. 
     
    
    
     DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS 
     A. Overview 
     A better understanding of different embodiments of the invention may be had from the following description read in conjunction with the accompanying drawings in which like reference characters refer to like elements. 
     While the disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments are shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the disclosure to the specific embodiments disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, combinations, and equivalents falling within the spirit and scope of the disclosure and defined by the appended claims. 
     It will be understood that, unless a term is expressly defined in this patent to possess a described meaning, there is no intent to limit the meaning of such term, either expressly or indirectly, beyond its plain or ordinary meaning. 
     Any element in a claim that does not explicitly state “means for” performing a specified function, or “step for” performing a specific function, is not to be interpreted as a “means” or “step” clause as specified in 35 U.S.C. §112, paragraph 6. 
     B. Environment and Context of Embodiments 
     Numerous embodiments of the invention are provided to reduce the effect of osteoarthritis in a knee joint, or stabilize a knee joint that has been weakened by injury or other infirmities. Embodiments of the invention may be configured to reduce or cure both medial and lateral knee joint infirmities. 
     Embodiments of the invention are particularly adapted for a human knee joint, and may be dimensioned to accommodate different types, shapes and sizes of human joints and appendages. In addition, embodiments may be modified to orient principal forces exerted by strap systems of the embodiments at any desirable location to treat knee infirmities. 
     For explanatory purposes, each knee brace embodiment described herein is divided into sections which are denoted by general anatomical terms for the human body. Each of these terms is used in reference to a human leg which is divided in similar sections with a proximal-distal plane generally extending along the meniscus of the knee between the femur and tibia. 
     In reference to  FIG. 3 , an embodiment of the knee brace orthotic device is divided into anterior and posterior sections by an anterior-posterior plane. The anterior-posterior plane generally corresponds to the coronal or frontal plane of a human leg. Each of the anterior and posterior sections is further divided about the center of the knee by a transverse or proximal-distal plane, and median, sagittal or lateral-medial plane. 
     Referring specifically to  FIGS. 4-6 , the anterior section of the knee brace of  FIG. 3  has the following quadrants: (I) proximal-medial, (II) distal-medial, (III) distal-lateral, and (IV) proximal-lateral. The posterior section of the knee brace of  FIG. 3  has the following quadrants: (V) proximal-medial, (VI) distal-medial, (VII) distal-lateral, and (VIII) proximal-lateral. 
     The anatomical terms described herein are not intended to detract from the normal understanding of such terms as readily understood by one of ordinary skill in the art of orthotics. 
     C. Various Embodiments of the Knee Brace 
     i. Overview of Knee Brace Embodiments 
     Referring to  FIGS. 7-10 , a knee brace embodiment 10 is shown. While this knee brace is particularly shown and configured for treating lateral osteoarthritis of the knee, it is understood that the knee brace may be configured by reversing the features in order to treat medial osteoarthritis of the knee. 
     According to this embodiment, the brace  10  includes a sleeve  12  covering or upon which various components and assemblies are secured. As will be described below in reference to proximal and distal frame elements or shells  40 ,  42 , these shells are connected to, inserted into, or secured against the sleeve to provide sufficient rigidity to the brace. 
     According to this embodiment, the sleeve  12  includes a breathable central strip portion  14  generally extending along the proximal-distal plane of the brace  10 , and a center ring  16  located approximately about the center of the sleeve  12 . The center ring  16  is preferably constructed from an elastic material so as to provide sufficient flexure of the brace  10  about the center portion thereof, and is located so as to assist a user of the device in placing the center portion over the anterior knee. Moreover, the portion of the sleeve  12  corresponding to the proximal portion of the knee is left exposed in order prevent interference of extension and flexion of the knee. 
     First and second force straps  18 ,  20  are each secured at a first end to a corresponding tightening device  22 ,  23  that protrudes out of an opening  24 ,  25  of the sleeve  12 . The second end of each of the force straps  18 ,  20  is secured to a corresponding bracket assembly  26 ,  27  also secured to the sleeve  12 . The first and second force straps  18 ,  20  intersect at intersection point  21  that is located near or along the proximal-distal plane on the posterior, medial side of the brace  10 . 
     Each of the force straps  18 ,  20  may include a cushion feature  36  that may be located near or at locations anterior or posterior of the intersection point  21 . Moreover, the force straps  18 ,  20  preferably each have a length adjustment feature  29 , such as a hook and loop fastener system, to enable adjustment of the length of such straps  18 ,  20 . 
     In this embodiment, the force straps  18 ,  20  are substantially inelastic in order to apply a greater amount of pressure against the knee as opposed to what may occur if elastic straps are used. It has been found that force straps having substantially elastic properties do not effectively unload a knee. Instead, elastic force straps pull the knee into flexion such that when the leg is straightened, the force straps resist flexure of the knee. As a result, while tightening the force straps may indeed unload the knee, the knee is unable to undergo full extension due to the tendency of the knee to go into flexion. Unlike the elastic straps, substantially inelastic straps do not possess these drawbacks since they draw the knee towards a hinge and unload the knee while permitting both flexure and extension of the knee. 
     It should be understood, however, that embodiments of the knee brace are not limited to usage of substantially inelastic straps. To the contrary, straps of various degrees of elasticity may be employed with the various components in different the embodiments of the knee braces to suit various needs of an individual wearing the brace. 
     The first force strap  18  is secured to a lateral-proximal bracket assembly  26  and spirals along the posterior of the brace  10  towards the medial-distal side of the sleeve  12 . The first force strap  18  then enters in the sleeve  12  and secures to a distal tightening device  23  generally located on the anterior-lateral, distal side of the sleeve  12 . 
     The second force strap  20  is secured to a lateral-distal bracket assembly  27  and spirals around the posterior of the brace  10  towards the medial proximal side of the sleeve. The strap  20  then enters the sleeve  12  and secures to a proximal tightening device  22  generally located on the anterior-lateral proximal side of the sleeve  10 . As will be described in the ensuing discussion, the proximal and distal tightening assemblies  22 ,  23  are provided to incrementally tension the first and second force straps  18 ,  20 , and selectively allow release of tension in the force straps  18 ,  20 . 
     A proximal stability strap  28  is secured to the medial side of the brace  10  and extends to the lateral side whereat it is connected to a proximal buckle assembly  32  that is connected to the sleeve  12 . A distal stability strap  30  is secured to the medial side of the sleeve  12  and extends to the lateral side whereat it is connected to a distal buckle assembly  33  which is also connected to the sleeve  12 . 
     According to this embodiment, each of the stability straps  28 ,  30  includes a cushion feature  34 , such as foam or a textile pad that is secured thereon for enhanced rotational prevention and additional comfort. The stability straps  28 ,  30  each have an adjustment feature  35 , such as a hook and loop fastener system, to enable adjustment of the length of such straps  28 ,  30 . Moreover, the cushion feature may include a frictional feature (not shown), such as a pattern of deposited silicone, rubber, or a mildly abrasive material. In addition, the cushion feature may be breathable, and have a construction similar to the spacer elements described below. 
     In one variation, the stability straps may be releasably secured to the knee brace. For example, the stability straps may include a snap fastener element that corresponds to a snap fastener element supported by shells of the knee brace. In another variation, other suitable releasable fasteners may be used to permit installation and removal of the stability straps from the knee brace. 
     An embodiment of the knee brace may be provided alternatively with one force strap connected to a tightening device and another strap that is adjustable with a fastener system such as hook and loop fasteners. For example, in the event that it is desired to provide a low profile brace, one could use a force strap system that is connected to and adjustable at the proximal portion (corresponding to the femur of the wearer) of the brace that includes a tightening device, whereas the force strap system connected to the distal portion (corresponding to the tibia of the wearer) may simply use a hook and loop fastener system. Variations of this embodiment are also useful in order to mitigate issues of a tightening device extending over pressure points that may be present over the tibia. 
     The embodiment of the brace of  FIGS. 7-10  is generally oriented to relieve lateral compartmental osteoarthritis of a left knee. This brace may be configured to treat medial compartmental osteoarthritis of the left leg or, in the alternative, medial or lateral compartmental osteoarthritis of a right knee. The reconfiguration for treating medial compartmental osteoarthritis comprises arranging the force straps in a reverse configuration so the force straps have an intersection point on the proximal-distal plane on the posterior-medial side of the device. 
     Turning to  FIG. 11 , the internal features of the embodiment of the brace  10  are shown in greater detail without the sleeve  12 . Of interest are the proximal and distal shells  40 ,  42  which provide the structure for brace, and connect to the force straps  18 ,  20  and the stability straps  28 ,  30 . Of additional interest are the proximal and distal spacer elements  46 ,  48  which provide anti-rotational means, such as a frictional feature, and cushioning for the brace  10  when worn on a leg. 
     The proximal and distal shells  40 ,  42  are configured for placement between the lateral and medial sides of an anterior portion of the brace  10 . Similarly, the proximal and distal spacer elements  46 ,  48  are configured with a shape generally corresponding to the proximal and distal shells  40 ,  42 , and are arranged for connection to a rear portion of the sleeve  12  in register with the shells  40 ,  42 . It is desirable that the proximal and distal shells  40 ,  42  be in register with the proximal and distal spacer elements  46 ,  48  so that as the force straps and stability straps are tensioned about a leg. The spacer elements  46 ,  48  are urged against a leg so as to prevent rotation of the brace  10  due to the forces applied to the leg from the force straps. 
     According to variations of the shells, they may be configured for placement on the posterior side of the brace, or at least have sections that extend over a portion of the posterior section of the brace. In addition, variations of the shells may involve one shell such as the proximal shell extending about the anterior side of the brace between the lateral and medial sections, whereas the distal shell extends over the posterior side of the brace and further includes a segment wrapping over at least one of the lateral and medial sides to cover a portion of the distal-anterior section of the brace. 
     A benefit of the spacer elements in a hingeless knee brace is that these spacer elements prevent migration of the shells towards one another. The spacer elements also maintain the knee brace on the user&#39;s leg due to anti-rotation means. Moreover, the spacer elements can also resist any rotational forces that may be applied by the force straps. 
     ii. Method of Applying the Knee Brace 
     In operation, the embodiment of the brace according to  FIGS. 7-11  is attached to the user, for whom it may be custom made or pre-fabricated, by positioning the device on the leg with the center portion of the sleeve placed over the anterior knee. The proximal and distal force straps  18 ,  20  are positioned above and below a side of the knee, and tightened accordingly. This arrangement of the force straps ensures that the force straps tighten above and below the knee as the leg moves into extension and loosens as the leg moves into flexion. The tightening of the force straps  18 ,  20  during extension of the knee prevents movement of the bone upon extension of the leg, and thus treats the adverse affect of compartmental osteoarthritis. 
       FIGS. 12 and 13  illustrate the brace on a left leg  11  that defines proximal and distal portions corresponding to the femur and tibia, respectively. The tightening of the force straps  18 ,  20  tend to depressurize the compartment of the knee by increasing the space between the bones on the affected side of the knee. The configuration of the force straps along the frame elements  40 ,  42  provides reaction points for the force straps  18 ,  20 . Thus, tightening of the force straps  18 ,  20  causes the frame elements  40 ,  42  in combination with the spacer elements to stabilize the knee on the side opposite the intersection area  21 . 
     From  FIG. 12 , the forces A 1  and A 2  are shown applied to the medial side of the knee at a greater degree than the single force A generated by the prior art braces, as exemplified in  FIGS. 1 and 2 , due to the greater distribution of pressure on the leg. Additional forces B are applied on the lateral side of the leg approximately where the force straps are attached to the proximal and distal members. By applying two forces, these forces counteract to mitigate the rotational moment that is present in the prior art braces wherein rotational forces Y R1  and Y R2  are generally equal to and cancel one another. 
     It has been found that if only one force strap is used without any intersecting points, as in the prior art braces, the skin and soft muscle tissue move with the shells. As a result, the unloading effect of the straps decreases significantly. By using the two force straps to form forces A 1  and A 2 , rotation of the device on the leg is reduced and effectively prevented. This provides a sufficient unloading effect by the brace on the knee. 
     The force straps are substantially inelastic since, as mentioned previously, it has been found that in prior art braces that employ elastic force straps, the knee and leg counteract the suppleness of the elastic straps thereby reducing the unloading effect on the knee. By using substantially inelastic force straps, the knee is unable to resist the straps and, consequently, a greater unloading effect is obtained of the knee. 
     Referring to  FIGS. 14 and 15 , the resultant force “A” of forces A 1  and A 2  in  FIG. 12  is applied as the knee goes into extension. The force straps preferably cross at intersection point  21  at angle α ranging about 5° to 20° posterior of the normal axis of rotation of the knee with the knee cap  51  being in front of rotational axis R and tibia  53 . The intersection point is preferably not the point of unloading; instead, the unloading point is directly on the lateral side for the medial brace, and directly on the medial side for the lateral brace. 
     The knee brace may be tailored to optimize the forces generated by the force straps. When the brace includes two force straps or has a single force strap with two intersecting portions, a greater moment is applied to a leg providing that the same force is now applied by two force straps. This results in a lower angle that may be used to configure the force strap(s), and consequently proximal and distal frame members or shells may be positioned closer together as opposed to in prior art braces having only a single cross-strap which spirally extends once between proximal and distal members. 
     In following discussion, descriptions and variations of the specific components pertaining to the inventive knee brace are described. 
     iii. Straps 
     The force straps and stability straps may be constructed from a variety of different textiles and other suitable materials. According to one variation exemplified in  FIGS. 16 and 17 , the force strap  400  and stability strap  412  are shown as comprising a two layer system; an inner core  404 ,  416  surrounded by an outer layer  402 ,  414 . Suitable stitching  406 ,  420  is provided to secure the inner core  404 ,  416  and outer layer  402 ,  414  together. When viewed from a rear end, the two layer system combines to form a C-folded strap wherein the outer layer  402 ,  414  wraps around the inner core  404 ,  416  to generally define an elongated C-shape about the corners of the strap. 
     The inner core  404 ,  416  is preferably constructed from a soft loop material. This material is generally soft to the touch so that for a knee brace orthotic device having the strap extend about the popliteal (back of the knee), the worn strap is comfortable to the wearer of the brace. This is evidenced when the wearer flexes his leg as well as when the leg is fully extended. The compliance and softness of the inner core mitigates the need for a cushion feature of the very type shown in  FIGS. 7-10 . 
     The outer layer  402 ,  414  may be constructed from any suitable textile since the compliance of the strap is essentially provided by the inner core  404 ,  416 . This enables the use of a cosmetically pleasing or a substantially inelastic material. 
     Both of the straps  400 ,  412  may include a tab  410 ,  418  located at the front end of the straps to provide adequate reinforcement to this area. The tab  410 ,  418  may comprise a plastic or metal piece that is secured to the front end of the straps by a press fit, stitching, adhesive or other suitable means. In addition, as will be discussed in further detail below, the force strap  400  may include indicia  408  representative of incremental settings of the strap. 
     In yet another variation, the stability straps may be substantially stretchable and secured to the sleeve or shells. The straps according to this variation may be configured so that they are dimensioned so as to permit the brace to be donned and doffed by being slidable on a leg of an individual wearing the brace, but sufficiently tensioned so as to wear tightly on the individual&#39;s leg. 
     iv. Shells 
       FIGS. 18 and 19  illustrate one variation of the proximal and distal shells  40 ,  42  of the brace of  FIG. 7 . Each of these shells  40 ,  42  has a perforated structure  52  which ventilates the brace and therefore mitigates heat build-up when the brace  10  is worn on a leg. Moreover, each shell has a clearance  50  which extends between the lateral and medial sides thereof as a further ventilation feature. While the shells  40 ,  42  are of sufficient rigidity and strength to withstand forces exerted by the force straps  18 ,  20  and the stability straps  28 ,  30 , the shells  40 ,  42  may be flexible to conform to corresponding portions of a leg. 
     Because the shells  40 ,  42  have a perforated structure  52  and a clearance  50 , the shells may be sized larger than other known structural features or frame members known in the knee bracing art. For example, the proximal shell  40  has an enlarged first side portion  54  that provides sufficient support against a leg and can accommodate the tightening device  22  and buckle assembly  26 . The shell  40  also defines a protruding section  56  extending from the first side portion  54  in a direction generally tracing the path of the second force strap  20  so as to distribute the pressure of the strap against the leg. 
     The shell  40  defines a second portion  58  that is sufficiently large to secure to a leg, yet is of minimal size to prevent excessive intrusion on a corresponding side of a leg. Similarly, the distal shell  42  defines features corresponding to the proximal shell  40 , such as an enlarged first side portion  68 , a protruding section  70 , and a second side portion  72 . 
     As exemplified in  FIGS. 20 and 21 , each of the shells  40 ,  42  preferably has provisions for mounting the tightening devices  22 ,  23 , the bracket assemblies  26 ,  27 , and the buckle assemblies  32 ,  33 . The shells  40 ,  42  may each include an opening  66  for receiving a mounting feature  82  of a tightening assembly, and an eyelet  62  located on the lateral portions  54 ,  68  which is arranged to receive corresponding pins or similar features  82  of the bracket assemblies  26 ,  27  and buckle assemblies  32 ,  33 . The eyelet  62  defines a seat portion  64  in which the mounting feature  82  of the bracket and buckle assemblies, such as a pin, button, flange, hook, or similar element, are urged and retained there against. The seat portion  64  is defined as a reduced portion of the eyelet  62  having a radius just larger than the mounting feature. Also,  FIG. 19  shows a similar construction with eyelet  63  and seat portion  65  on the shell  42 . 
     The construction of the eyelet of this embodiment is particularly advantageous in that it facilitates detachment of the buckle assemblies and bracket assemblies from the device when not worn on a leg. For example, when the force straps and stability straps are de-tensioned, or the brace  10  is not worn, the mounting feature  82  may be urged from the seat  64 , and subsequently removed from the shells  40 ,  42 . However, when the straps are in tension, the mounting feature is urged and locked in register with the eyelet seat  64 . 
     In a variation of this embodiment, individual eyelets of the type described above may be defined on the shells for individually accommodating both a buckle assembly, and a bracket element having a mounting feature. According to another variation of this embodiment, either of the buckle assembly or bracket element may have a hook which is securable against a corresponding eyelet defined in the shells. In yet another variation of this embodiment, the bracket element and buckle assembly may be permanently secured onto the shells using means such as rivets or other known fasteners. 
     In accordance with another variation of the shells,  FIGS. 22 and 23  show proximal and distal shells  422 ,  448  having a different perforated structure  424  from the embodiments of  FIGS. 18 and 19 . Specifically, the perforated structure  424  comprises a plurality of generally horizontal slots  426  extending along segments across the width direction of the shells  422 ,  448 . These slots  426  are interspersed with a plurality of slats  428  or are generally laterally spaced by material segments  438 . Frame portions  430  of each of the shells  422 ,  448  surround the slots  426  and slats  428 . 
     The shape of the proximal shell  422  generally resembles the shape of the proximal shell shown in  FIG. 18 . Particularly, the proximal shell  422  defines a second side portion  432  that extends downwardly from a transverse portion  434  corresponding to the anterior-proximal portion of the shell and spanning to a first side portion  436 . The transverse portion  434  includes an arcuate profile that is preferably pronounced on the distal side thereof and conforms to the anatomy of a thigh. The first side portion  436  extends downwardly beyond the distance extended by the second side portion  432 , and is generally wider in size than the second side portion  432  to provide additional support on the leg. 
     The proximal shell  422  includes an eyelet  440  located on the second side portion  430 . The eyelet  440  is configured for receiving a pin or locking device of a buckle assembly. A seat  442  is located on a side of the eyelet that is preferably distant from the second side portion  432  of the shell. The seat  442  may form a slot extending from the eyelet  440  and has a smaller diameter than the eyelet  440 . 
     The proximal shell  422  also includes a slot  444  that is separate and larger than the slots  426 , and is located near the transition between the first side portion  436  and the transverse portion  434 . Preferably, the slot  444  is directed at an angle relative to the slots  426 . The slot  444  includes a compliant edge  445  that is located at a side thereof closest to the transverse portion  435 . The complaint edge  445  imparts a smaller effective height for the slot  444  and is arranged for receiving a pin, knob or other securing means carried by the ratchet assembly, as described more fully connection with  FIG. 43 . 
     The compliant edge  445  is formed of a material that is preferably more flexible than the material used to form the proximal and distal shells,  422 ,  448 . For the example, the compliant edge  445  may be a silicone rubber or a suitable polymeric material. 
     The proximal shell  422  also includes a slot  446  that is located at the second side portion  432  of the shell. Similarly, the slot  446  is located at an angle relative to the slots  426  and likewise includes a compliant edge  447  that is located at an end portion remote from the transverse portion  434 . 
     The shape of the distal shell  448  differs from the shape of the distal shell  42  shown in  FIG. 19 . Specifically, the distal shell  448  includes a second side portion  450  that connects to a transverse portion  452  corresponding to the anterior-proximal portion of the shell. The transverse portion  452  has a proximal arcuate profile  453  that is generally contoured to the shape of a shin of a human leg. From the transverse portion  452 , a proximal side of the distal shell rises to apex  455  which provides additional support to the wearer at a first side portion  454  of the shell  448 . The shell  448  also includes a calf extension member  456  that protrudes from the second side portion  454  of the shell  448 . 
     The calf extension member  456  extends to the posterior section of the brace when worn on a leg. The calf extension member  456  has the benefit of preventing the shell  448  from rotating when the knee brace is worn on a leg, and also serves as an additional suspension feature since it is preferably configured to extend over the thickest point of a human calf. Another benefit of the calf extension member  456  is that it removes the necessity of two stability straps for connection to the distal shell since the calf extension member effectively provides substantial support about the calf. 
     The distal shell  448  includes an eyelet  458  that has a seat portion  460  which is similarly constructed as the eyelet  440  and seat portion  442  of  FIG. 20 . The distal shell also includes a slot  462  and a corresponding compliant edge  463  that generally corresponds to the same location with the exception of their orientation as the slot  444  and respective rim  445  in  FIG. 20 . Also, the distal shell has a slot  464  and a respective compliant edge  465  that corresponds in location with the exception of orientation to the slot  446  and respective rim  447  in  FIG. 20 . 
     The shells  422  and  448  may include a compliant feature  470  disposed about the entirety or at least portions about their periphery. The compliant feature is constructed of a material that is more flexible than the material comprising the shell bodies. The compliant feature  470  extends beyond the outer perimeter of the shells. The compliant feature is preferably a flexible resilient material that is secured to the shells by bonding, mechanical interlocking or any other suitable arrangement. An example of a method for providing the compliant feature is described in U.S. Pat. No. 5,445,602, incorporated herein by reference. 
     The shells may be custom sized and contoured to accommodate the leg of a wearer of the brace. Also, the shells may be preformed to curve to the contour of a leg, or curved as a result of the straps and sleeves causing the shells to curve about the leg of a wearer of the brace. While the embodiments described herein assume the shells to be sufficiently flexible to accommodate a wearer&#39;s leg in both extension and flexion of the knee, the shells can also be configured to be substantially rigid as in prior art braces. 
     The proximal and distal shells of these variations may be constructed of variety of materials such as TRIAX (abs/nylon blend), polypropylene, polyethylene, nylon, carbon or glass fiber prepeg with thermosetting or thermoplastic resins, and rigid foam from EVA, platezote or polyurethane. In another variation, the proximal and distal shells may be constructed similarly to the orthotic sleeve described in U.S. Pat. No. 6,592,539 assigned to Ossur hf of Reykjavik, Iceland, and incorporated herein by reference. 
     The perforated structure of the shells enables the shells to be sized larger than most frame members used in knee braces. As a result, the pressure exerted against the leg by the force straps can be more evenly distributed about the leg. 
       FIGS. 24-27  schematically show how the shells of the aforementioned embodiment of the knee brace are advantageous over those in known knee braces.  FIG. 24  schematically shows a hypothetical horizontal force F a , corresponding to the direction of a force strap, extending from a midpoint of a prior art shell  39 . In this arrangement, pressure from the force F a  is evenly distributed across the shell  39  and across leg  13 .  FIG. 25  shows hypothetical horizontal force F b  extending from a distal portion of shell  39 . In this arrangement, the force F b  exerts greater pressure across the leg  13  at the bottom of the shell than at the top of the shell. 
       FIGS. 26 and 27  more aptly exemplify the actual force exerted by a force strap on a proximal shell.  FIG. 26  shows a shell  39  in the prior art having a small size in order to minimize weight of the brace and the generation of heat due to the shell being worn against a leg. Because the shell is small, the force strap is secured to a center portion of the shell and diagonal force F c  creates greater pressure on a lower portion of the shell across the leg  13  than at the upper portion. 
       FIG. 27  shows shell  40 , wherein due to the ability to provide a larger shell, the force strap can be mounted at the upper portion of the shell. This results in diagonal force F d  which corresponds to a greater portion of the shell than the force F c , and thereby more evenly distributes pressure from the force F d  over the shell and across the leg  13 . By placing the force strap above the middle portion of the shell, one can obtain better distribution of pressure over the shell. 
     It has been found with known prior art knee braces that when force straps are not located at the same positions at both proximal and distal frame members, rotation of the frame members may occur. Since these frame members have a tendency to be significantly smaller than the shells according to the aforementioned knee brace embodiment, they are often located closer together, and proximate to the knee. 
     Particular benefits of the shells of the aforementioned embodiment are discussed in the following examples. In these examples, it is assumed that a force strap is provided which is pulled with a 10 N force, and the width of the knee or distance x is the same. In the first instance, the distance Y, which is defined as the distance between the shells, is 6 units. By moving the distance Y to 8 units, a greater moment due to the leverage arm is formed by the distance of the shells. Because of the increase in distance Y, the vertical force caused by the force strap is increased as a result of the change in angle of the force strap. Consequently, the shells are more strongly urged towards one another. On the other hand, the horizontal force is reduced so that the pressure on the knee in the horizontal direction is reduced, even though there is a greater moment applied to the knee. 
     It follows that if the shells are moved closer together, for example back to 6 units in distance, the moment is reduced yet there is more horizontal pressure on the knee. Moreover, the force exerted by the force strap must be increased in order to achieve the same amount of moment as created when the shells are separated by 8 units which results in yet more horizontal force about the knee. By providing the dual force strap arrangement, it is readily evident that the dual force strap provides two points of pressure and two straps creating a load on the knee. Therefore, the knee brace is more comfortable when unloading a knee since there is greater pressure distribution. 
     In addition to the advantages of the shells regarding pressure distribution, the shells can be arranged to extend over a greater portion of the leg than in known frame members. For example, prior art braces have small frame members that extend minimally about the leg, and the frame members have a tendency to rotate about the knee when the force straps are unloading the knee. This results in minimal tibia hyperextension and ligament control. 
     v. Sleeve 
       FIGS. 28 and 29  illustrate an embodiment of a sleeve  12  and the spacer elements  46 ,  48  that form proximal and distal pockets  84 ,  86  therebetween. The pockets  84 ,  86  include proximal and distal openings  74 ,  76 . The openings  74 ,  76  may be closeable with closing means such as hook and loop fasteners, zippers, buttons, and other suitable means. The openings  74 ,  76  are configured for permitting insertion of the shells  40 ,  42  into the pockets  84 ,  86  which are shaped to closely conform to the shape of the respective shells  40 ,  42 . The sleeve  12  further defines proximal and distal eyelets  78 ,  79 , which correspond to the proximal and distal eyelets  62 ,  63  of the shells  40 ,  42 . 
     In a variation of the embodiment of  FIGS. 28 and 29 , the sleeve includes pockets within the sleeve itself, wherein the shells are insertable into the pockets, and the pockets are closeable with a suitable fastener feature, such as with hook and loop fasteners, stitching, rivets, and other known means readily available to a skilled artisan. The spacer elements are secured against a rear portion of the sleeve corresponding in shape and location to the shells. 
     In another variation, the sleeve and spacer elements may be secured to one another so that the pockets form at the lower side of the proximal section and the upper side of the distal section. According to this variation, the shells may be inserted into the pockets so that the spacers and sleeve effectively cover the shells, yet so that the shells are easily removed from the sleeve and spacers. This also enables the shells to slide into the pockets while the shells are still connected to one another. 
     In yet another variation, the shells may be secured, either permanently or removable, to the posterior side of the sleeve with a suitable fastener feature. In yet another variation, the brace may be provided without the sleeve, and simply possess the structure shown in  FIG. 11 , wherein the spacer elements are secured to the shells by a suitable fastener feature. A hinge may be used to connect the shells, or other suitable connecting elements may be used to prevent the shells from being drawn towards one another when the brace is provided without the sleeve. 
     In yet another variation of the sleeve, the sleeve comprises proximal and distal portions that are separate from one another. According to this variation, the proximal and distal portions may include the aforementioned pockets for retaining the shells, or in the alternative, the shells may be secured to a surface of the sleeve portions. According to this variation, the sleeve portions may be connected by a hinge located on one of the lateral or medial side of the brace, or with one of the other connecting element described herein. 
     Another variation of the sleeve is shown in  FIG. 30  wherein the sleeve  242  is configured for enveloping frame elements and is removable therefrom. According to this variation, the sleeve  242  generally conforms to the outer surfaces of the proximal and distal members, and preferably envelopes the outer surfaces of the aforementioned features of the knee brace. The sleeve  242  includes an opening  246  that generally corresponds to an anterior knee. This provides access to the knee cap and is located at a portion of the sleeve that is subjected to bending of the knee. 
     Encircling the opening  244  is a first beveled portion  246  that eases the flexion of the sleeve  242  during gait. In addition, the sleeve  242  is provided with a second beveled portion  248  disposed along the proximal and distal edges. The first and second beveled portions  246 ,  248  relieve the brace of any sharp or blunted edges that may catch on clothing, and are thus provided to facilitate the donning of clothing over brace. 
     The sleeve  242  may be applied over the underlying features of the knee brace in a variety of manners. According to the variant shown herein, the sleeve  242  takes the form of a socket that surrounds the underlying features. Also, the sleeve  242  may include pockets wherein proximal and distal shells may be inserted therein, and means on the exterior of the sleeve for securing spacer elements. The sleeve may be unrolled from a rolled up condition for donning over the underlying features, and is secured thereon due to elasticity of the sleeve or, in the alternative, by hook and loop fasteners or other suitable means. 
     The sleeve  242  may include a zipper  290  located along one side of the proximal section thereof. As shown in  FIG. 31 , the zipper  290  provides an access  292  to a tightening mechanism  295  secured to a proximal shell  293  and a force strap  294 . This particular variation allows for concealment of the tightening mechanism  295  under the sleeve  242 , yet still permits facile access for adjusting the tightening mechanism. Moreover, this variation prevents the tightening mechanism from catching on clothing or any other objects that the leg may come into contact with, and further provides for a more cosmetically pleasing brace. The proximal portion of the sleeve can have a similar zipper and access to the distal shell. 
     The sleeve may be constructed of a fabric including spandex, lycra, nylon, polyester, OUTLAST, COOLMAX, AEROSPACER, microfiber, three-dimensional fabrics, and other suitable fabrics. The sleeve may have various treatments incorporated therein such as antibacterial, scenting, and moisture wicking agents. 
     In yet another variation of the sleeve, the sleeve may be constructed as the orthotic sleeve in U.S. Pat. No. 6,592,539 wherein elasticized fabric is used to form the sleeve and is arranged in different sections that exhibit different elastic stiffness in lengthwise and widthwise directions of the fabric. That is, the fabric is essentially stiffer in one direction than in a direction perpendicular to the one direction. 
     vi. Spacers 
     As shown in  FIGS. 11 and 29 , the brace  10  includes proximal and distal spacer elements  46 ,  48  that are contoured in a similar configuration as the shells  40 ,  42 . These spacer elements  46 ,  48  are arranged so as to be breathable by permitting a free flow of air therethrough. The spacer elements also preferably include a friction feature on at least one side thereof. 
     The spacer elements may be connected to the sleeve via removable means, such as with a hook and loop fastener system, or may alternatively be secured to the sleeve via stitching, adhesives, or other similar fastener features. While the spacer elements are intended not to interfere with the motion of the knee, they are intended to provide sufficient frictional force to maintain the shells against the knee due to the vertical forces created by the force straps. 
     According to this embodiment, the spacer elements  46 ,  48  are secured to the posterior side of the sleeve  12 . The spacer elements  46 ,  48  have a breathability feature  88 . According to a variation, the breathability feature comprises a pattern of openings defined across the spacer elements  46 ,  48 . Alternatively, the breathability feature may comprise a breathable fabric, and may be combined with a pattern of perforations to further enhance the breathability of the spacers. Moreover, the spacer elements may be constructed from a material that provides cushioning and further compresses, at least in part, when the brace is worn. 
     As shown in  FIG. 32 , the spacer elements  46 ,  48  preferably have a friction feature  92  that is coated on at least a posterior surface of a substrate material  90  that forms the body of the spacer elements  46 ,  48 . This friction feature  92  has a high frictional coefficient against the skin or clothing. Moreover, the friction feature  92  does not occlude the breathability feature  88  of each spacer element  46 ,  48 , and permits a transfer of air through the spacer elements. 
     According to this embodiment, the spacer elements have a mesh or core portion  94  that permits the passage of air therethrough, and yet is compressible to provide adequate cushioning and securing to a leg when placed in tension. In addition, the spacer elements have a reinforced edging  96  provided to protect the core portion, and enhance the durability of the spacer elements. 
     In another variation, as shown in  FIG. 60 , the spacer elements may be directly connected to the shells. Of course, such spacer elements may be configured so that they may be removed from the shells and reapplied without harming their structure. Fasteners such as hook and loop systems may be used to attach the spacer elements to the shells. 
     Preferred substrate materials that may be used to form the spacer elements include foams, neoprene, and textiles. While numerous materials may be used as the spacer elements, it is desirable that these materials have a three-dimensional knit structure covered by a mesh that provides sufficient breathability, insulation, compression, durability, and recovery. An exemplary material is produced by Gehring Textiles under product numbers SHR 701, SHR 714 or SHR 754F. 
     According to this embodiment, the posterior surfaces of the spacer elements are coated with the friction feature which comprises a continuous, discrete layer of cured silicone elastomer material  92 . The silicone elastomer material is preferably sufficiently thick and soft to be comfortable to the user, and yet provides a seal between the proximal and distal members, and the skin or clothing of a user of the brace  10 . The silicone coating preferably has apertures which correspond to apertures of the mesh surface of the three-dimensional fabric when such a fabric is used to form the substrate of the spacers. In a variation, the silicone coating may comprise a plurality of dots which are deposited to the surface of the substrate of the spacers. 
     The silicone material may be mixed with scenting, anti-inflammatory, anti-bacterial, and coloring agents. Moreover, the silicone material may include skin friendly agents such as aloe vera or Vaseline. A more complete description of additives to the silicone may be found in U.S. Pat. No. 6,485,776 assigned to Össur hf and incorporated herein by reference. 
     The silicone elastomer preferably has a Shore hardness of 25-70; a minimum tensile strength of 230 lbs/inch; a 100% modulus of 8 psi; a 500% modulus of 61 psi; a minimum tear strength of 49 lbs/inch; a maximum strength of 500 lbs/inch and an elongation of about 1000%. 
     The silicone elastomer coating may be disposed in a uniform thickness in both circumferential and longitudinal directions, or may have a varying thickness to accommodate varying shapes of a leg, protrusions, contours, etc. The coating may also be configured to have a specific relief from localized pressure that may result from installation of the proximal and distal members on a human leg. 
     While the spacer elements are preferably coated only on their posterior surfaces, the anterior surfaces of the spacer elements may likewise be coated so as to frictionally couple with the sleeve. In the alternative, the friction elements may be constructed of sections of elasticized fabric and coated with silicone of the type described in U.S. Pat. No. 6,592,539. 
     In a variation of the brace, the brace does not include the spacer elements and instead relies on the proximal and distal member straps for attachment to a user. In another variation, the spacer elements that are not coated with silicone. These spacer elements provide a compressive buffer between the proximal and distal members and a leg of a user of the brace. In yet another variation, the substrate may comprise a textile having superior frictional properties, and as a result, merely the compression of the textile is sufficient to prevent rotation of the brace when worn on a leg. 
     In yet another variation, the spacer elements may comprise a silicone mesh comprising a textile that is impregnated with silicone. This silicone mesh defines a pattern of apertures that permit the transport of air therethrough. In yet another variation, the spacer elements form a silicone sheet having a pattern of apertures, and sufficient thickness to serve as a buffer between the sleeve, frame members, and a leg. 
     vii. Tightening Device 
     Turning to another component of the brace, the brace includes a tightening device  22 ,  23  that is provided for adjusting the tension of the force straps  18 ,  20 .  FIG. 33  schematically illustrates one embodiment of the tightening device as a ratcheting system  98  that permits tightening and release of a cable  102  connected to the force straps  18 ,  20 . An end of the force strap  20  is secured to a ring  100  that is fixed to the cable  102 . The tightening device  32  is configured to incrementally provide or release tension to the cord  30 . 
     According to this embodiment, the cable  102 , ring  100  and end of the force strap  20  are contained within the sleeve  12 . It will be understood that in alternative embodiments, the cable, ring and force strap may be at least partially or completely outside the sleeve. 
       FIG. 34  illustrates an embodiment of a ratchet assembly  98  connected to the cable  102  and the ring  100 . In this embodiment, the cable  102  departs from a ratchet body  106  through opening  116  and secures at one end to a seat  104  defined on the ring  100 . The ratchet assembly  98  includes a rotatable handle  108  that is indexed to indicia  110  defined on the body  106 . A button  112  is slidable within slot  114  and permits release of the ratchet assembly. According to this embodiment, the handle  108  rotates as the cable  102  is unwound from the ratchet assembly  98 . 
     The handle  108  provides mechanical leverage and provides independent use and adjustable security. The indicia  110  enables a user to measure and control the degree of rotation of the handle  108 , and thus determine the extent of the force applied on the knee by the force strap. The handle  108  is pivotable so as to place the ratchet assembly  98  in a low profile configuration when the handle  108  is not in use. 
     The internal mechanism of the ratchet assembly  98  is shown in  FIG. 35 . In this embodiment, the body  106  contains a ratchet wheel  126  having a plurality of teeth, and a spool  127  which are mounted to rotate together on axle  128 . A pawl  118  is mounted on axle  124 , and has first and second portions  120 ,  122  extending from the axle  124 . The first portion  120  connects to the button  112 , and the second portion  122  extends obliquely relative to the first portion  120  and engages teeth of the ratchet wheel  126 . 
       FIG. 36  depicts another embodiment of the tightening device that may be used in the knee brace. According to this embodiment, a ladder strap  130  has a buckle  138  which secures to an end of the strap  20 . A lever  136  is pivotably secured to the shell  40  and engages one of numerous grooves  134  of the ladder strap  130 . The grooves  134  may be provided with indicia that correlate to a degree of tensioning of the strap  20  against the knee. 
     Preferably, the lever  136  is biased towards the ladder strap  130 . A first end of the lever  136  engages one of the grooves  134  of the ladder strap  130  and secures the ladder strap  130  from movement relative to the shell  40 . Of course, if pressed at a second end opposite the first end, the lever  136  is released from one of the grooves  134  and the ladder strap  130  may be adjusted relative to the lever  136  accordingly. 
     In this embodiment, the ladder strap  130  includes a grasping element  132  in the form of a ring formed at an end opposite the connection to the strap  20 . As better exemplified in  FIGS. 7 and 8 , the grasping element  132  is intended to extend outwardly from the sleeve  12  so as to provide access to a user of the brace. Moreover, the latch  136  may extend outwardly from the sleeve  12  so as to facilitate adjustment of the ladder strap  130  and to permit an indication as to which groove  132  the lever  136  engages. 
     The ladder strap is preferably formed from a resilient material and may flex to have a curvature that generally corresponds to a leg of a wearer of the brace. The grasping element is not limited to a ring, and may be formed or comprise a variety of known constructions that permit easy handling for a user of the device. While the grooves of the ladder strap are shown as having a generally oval shape, it will be appreciated that other shapes or configurations are possible such as saw tooth teeth, rectangular teeth, and symmetrically triangular teeth. 
     According to one variation, the latch has a protruding forward end oriented with a bias towards the groove of the ladder strap in order to improve the latch&#39;s ability to positively engage one of the grooves of the ladder strap. The protruding forward end is preferably sized and configured to engage each of the grooves on the ladder strap. 
     The latch body may be pivotable between an engaged position wherein the forward end of the lever engages the grooves of the ladder strap, and a return position wherein the forward end of the lever is slidable over the grooves. In the engaged position, the protruding portion of the forward end of the latch functions as a pawl for the ladder strap. An internal biasing mechanism, such as a torsional spring, may be used to bias the protruding portion of the forward end towards the engaged position. The lever may have portions that are cutout, which not only lighten the lever by reducing the amount of material required, but also provides access to the area underneath the lever. 
     According to a variation of the tightening device of  FIG. 36 ,  FIGS. 37-40  illustrate a ladder strap compliant mechanism  500 . In this mechanism, the latch  504  is resiliently biased towards the ladder strap  502 . 
     The latch  504  defines opposed arms  522  which form part of an upper mount  512  that is secured to a lower mount  514  positioned on a base  506 . The arms  522  are sufficiently compliant to withstand torsion in the event a rear end  526  is depressed to disengage a detent  516  located at a front end  524  of the latch  504  from the teeth  510  of the strap  502 . 
     The ladder strap  502  defines a grasping element  508  defined at a forward end and a plurality of teeth  510  which permit incremental adjustment of a force strap. The strap  502  also defines a rear end  520  that flares in width. The latch  504  is positioned relative to the strap  502  so that the latch lies between the grasping element  508  and the rear end  520 . This is so as to prevent the rear end  520  from passing through the latch  504  and to establish a maximum distance that the grasping element  508  may be drawn from the detent  516 . 
     The base  506  is provided for mounting the latch  504  and for which the strap  502  slides thereon. The base  506  includes apertures  518  for mounting onto shells of the knee brace. 
     The tightening device  500  may be constructed from a variety of flexible and resilient materials including plastics, metals and composites. Moreover, the strap  502 , latch  504  and base  506  may be constructed from different materials. 
     In a variation of the base  506  according to  FIGS. 37-40 ,  FIGS. 41-43  illustrate another base  528  having additional features to those of base  506 . According to this variation, the base  528  is integrally formed with arms  530  that in turn are integrally formed to the latch  529 . As with the embodiment of  FIGS. 37-40 , the latch  529  is resiliently biased towards the base  528 , and includes detent  516 . 
     The base  528  includes guard portions  534  that extend along the edges of the base  528  from the arms  530 . These guard portions act to prevent a ladder strap from shifting laterally with respect to the detent  516 . 
     The latch  529  includes a dosage meter  532  that indicates the relative position of a ladder strap to the base  528 . The latch may also include indicia  537  that indicate a release button  536  which protrudes from the latch  529 . 
     The base  528  includes a compliant edge  531  provided about the periphery thereof. Methods for supporting methods for making the compliant edge include those described in U.S. Pat. Nos. 5,445,602, 5,713,837 and 6,024,712 which are incorporated herein by reference. The compliant edge provides conformity to the anatomy of a wearer of the brace in that the impact of the edges of the base  528  are lessened against the wearer of the brace. 
     The compliant edges are relatively thinner than the base  528  and substantially more flexible than the material forming the base. The compliant edge is formed onto the base by being molded of plastic or other flexible material in a single molding step and secured together. Also, as indicated above, a compliant edge or edge portions may be provided for the shells of the knee brace wherein the compliant edge or edge portions are provided about the periphery of the shells in order to permit the edges of the shells to conform better to the anatomy of the wearer of the brace. 
     The embodiment of the base according to  FIGS. 41-43  also includes an array of holes  533  that are arranged to receive a knob (as shown in  FIG. 42 ) for securing to the shells. Each of the holes  533  includes a rim  535  that frictionally secures against the knob. The array of holes permit the selection of placing the knob in one of the holes to effectively lengthen or shorten the distance between connection to the shells and the latch  528 . 
       FIG. 44  illustrates the base  528  assembled with another embodiment of a ladder strap  539 . In this assembly, the knob  538  is secured within one of the holes  533 . The ladder strap  539  includes a plurality of indicia  542  identifying the teeth  541  of the strap  539 . The ladder strap  539  also includes a plurality of apertures  543  located at an end opposite the grasping element  545 . The plurality of apertures  543  are arranged to support threads, rivets or other fastening means that secure a force strap thereto. 
       FIG. 45  illustrates the ratchet assembly of  FIG. 44  secured to the proximal shell  422  of  FIG. 22 . In this embodiment, the knob  538  is secured to the rim  445  of the slot  444 . The security of the knob  538  with the slot  444 , and hence the frame  422 , allows for the tightening of a force strap  546  that is connected to the ladder strap  539  which in turn is engaging the base  528  of the ratchet assembly. As shown, the base  528  extends under the frame  422  so that the knob  538  can project through the slot  444  and secure to the rim  445 . 
       FIGS. 46-48  exemplify a ratchet assembly sharing some features with the ratchet assembly of  FIG. 44  and further includes a mounting system for maintaining the ladder strap  539  close to the base  528 . In this example, the mounting system comprises a pin and slot system such that the ladder strap  539  forms a pin  572  that extends through a slot  576  longitudinally formed along the base  528  and a perforated tab  580 . The pin  572  includes a flanged portion that is sized larger than the slot  576  and is adapted to fit through opening  578  disposed at a forward end of the slot. 
     The ladder strap  539  also includes a raised portion  574  with suitable apertures  582  for mounting to a force strap. This arrangement is advantageous in that the strap may be mounted generally parallel with the teeth  541  of the ladder strap  539  so as to align the forces and provide greater stability. 
     The mounting system is particularly provided for assuring that the ladder strap  539  remain in close proximity to the base  528  and facilitate the ratcheting thereof. This is of particular benefit in the event that the base is custom molded to conform to the leg of a patient when the ladder strap is not molded. Of course, this embodiment is merely exemplary of a mounting system and other mounting systems may also be used to effectively stabilize the ladder strap relative to the base, and hence the leg of a knee brace wearer. 
       FIG. 49  shows another variation of a tightening device that may use in the knee brace of this application. According to this embodiment, the force strap  20  is mounted outside the sleeve  12  or onto a frame member, and the force strap is secured to a bracket  146  at an end thereof which is connected to a ladder-type strap  142 . The ladder strap  142  defines a plurality of transverse teeth or protrusions  144 . A latch  140  is mounted to the sleeve  12  or a frame member in a manner similar to the embodiment of  FIG. 36 , which engages the teeth  144 . While this embodiment does not show indicia for each position the strap is tightened relative to the sleeve  12 , the teeth may be shortened and have a width that is less than the width of the ladder strap  142 . Indicia may be provided alongside each tooth of the ladder strap. 
     According to yet another variation, loop material is secured onto a strap and hook material is secured onto a corresponding shell. Alternatively, a plurality of rings are provided on the shells through which the force straps pass through. The force straps include hook and loop portions that correspond to one another and permit maintaining the force straps in place. 
     Commercial examples of a tightening device that may also be used with different embodiments of the knee brace include the BOA lacing system of BOA Technology Inc. of Steamboat Springs, Colo., or in the alternative a ratcheting buckle in combination with a ladder strap that is sold by M2 Inc. of Winooski, Vt. under product name 1” Mechanical Closure System (part numbers RB502 &amp; LS 118-WB). 
     In any of the embodiments concerning the tightening device, it is intended that the tightening device provide precise adjustment, whether incremental or not, of the force straps, and possess a sufficiently robust construction to withstand the tensile stress of the force straps. Different configurations of hook and loop fastener systems, buckles, straps, cords and ratchets are clearly envisioned as being used in the tightening device so as to provide simple adjustment and effective adjustment of the force straps. 
     viii. Strap Attachment Piece 
     An embodiment of a strap attachment piece  560  is shown in  FIGS. 50-52 . According to this embodiment, the piece  560  includes a generally triangular body  562  forming a neck  570  having a knob  564  that is formed at a first end of the body  562 . The knob  564  includes a tapered head portion  572  that facilitates securing the knob  564  onto one of the slots of the frame members, for example slot  446  of  FIG. 22 . 
     A plurality of apertures  566  are defined between second and third ends of the body  562 . Each of the apertures  566  includes a tapering portion  568  beginning from the side of the body  562  including the knob  564  to preferably the opposed side of the body  562 . The tapering portion  568  eases the pressure exerted onto body  562  by stitching, rivets, pins or other suitable means useable for securing straps to the piece  560 . 
     Referring back to the brace in  FIGS. 7 and 8 , the brace includes the buckle assemblies  32 ,  33  that connect to the stability straps  28 ,  30 . It is preferred that the buckle assemblies  32 ,  33  generally have a low profile so that they do not protrude greatly from the sleeve. Moreover, the buckle assemblies should be relatively simple to use while having an anatomically conforming shape and providing sufficient leverage to tightly secure the stability straps against the leg. 
     ix. Buckle Assembly 
     In an embodiment of the buckle assembly shown in  FIGS. 53-55 , a low profile buckle assembly is provided which locks the stability straps  28 ,  30  in position relative to the shells  40 ,  42 . This embodiment includes bracket  148  that secures to the strap  20  and connects to an arm  150  having a forward end  152  slidably engaging a lever body  154 . The arm  150  extends through a clearance  160  defined by the lever element  154  and has protruding elements  158  that engage with edges of the lever body  154  defining the clearance  160  that extends from a forward end  166  to a rearward end  164  of the lever body  154 . As a result of the construction of the lever body  154 , and its relationship to the arm  150 , the arm  150  is slidably connected to the lever body  154 . 
     A base element  156  is pivotably connected to the rearward end  164  of the lever body  154 . The base element  156  includes receiving holes  162  that are configured to receive the protruding elements  158  of the arm  150 , and a locking feature  158  for securing onto one of the shells  40 ,  42 . According to this embodiment, the locking feature is a button body having a head portion  168  with a diameter greater than the rest of the button body. The head portion  168  is intended to have a diameter greater than the seat portion  64  of the eyelet  62  defined on the shells  40 ,  42 . 
     The lever element  154  is pivotable between a disengaged position shown in  FIG. 53  and an engaged position shown in  FIG. 55 .  FIG. 54  shows an intermediate position between the disengaged and engaged positions. In the engaged position, the forward end  164  of the lever element  154  is brought against surface  170  of the base element  156 , and the arm  150  rests upon the surface  170  with the protruding elements  158  engaged with the receiving holes  162  of the base element  156 . 
     Preferably, the protruding elements  158  are resiliently urged into the receiving holes  162 . In the disengaged position, the lever body  154  is pivoted away from the surface  170  of the base element and the protruding elements  158  are removed from the receiving holes  162 . The arm  150  may be positioned between the forward end  166  and rearward end  164  of the lever body  154 , and a pin (not shown) may be located at the connection. 
     The bracket  148  includes a ring  172  for the strap  20  to extend through. In this embodiment, the strap  20  has a hook and loop system permitting an end portion  174  of the strap  20  to secure to a receiving portion  176  of the strap  20 . A user may set an approximate desired length of the strap using the hook and loop system prior to securing the buckle assembly. Subsequently, the buckle assembly is placed in the engaged position so as to securely place and secure the knee brace on the leg. 
     The buckle assembly includes a curved profile such that it conforms to the leg of a wearer of the brace. This imparts a more streamlined buckle assembly and further prevents buckle assembly from snagging on clothing or acting as an impediment to the wearer of the brace. 
     Another variation of a buckle assembly  188  is depicted in  FIGS. 56-58 . In this variation, the base element  193  and the bracket body  191  are connected to one another, thereby reducing the amount of parts and simplifying donning of the bracket and buckle to the shells. 
     As with other variations of the bracket assembly, the bracket body  191  includes a clearance  192  arranged for receiving a strap. The buckle portion of the assembly  188  is similarly arranged as in the embodiments of  FIGS. 53-55  in that it includes common features such as the base element  189 , lever body  190 , arm  193 , protruding element  197 , and bracket  191  having the clearance  192 . 
     The buckle/bracket assembly  188  has a securing feature located at the end portions of the base element  189  and the lever body  190 . Specifically, the base element  189  carries a recess  199  upon which a hook  198  formed from the lever body  190  secures thereonto. The hook  198  is biased to extend into the recess  199  and urge against the base element  189 . The hook  198  is also resilient so that it can deflect when the lever body  190  is urged away from the base element  189 . 
     The buckle assembly  188  also includes a bracket  195  which extends obliquely relative to the base element  198 . The bracket  195  includes a clearance  196  that is arranged to receive a force strap. The buckle assembly  188  has a curved profile that is similar to the curved profiles of the buckle assembly of  FIGS. 53-55 . 
     In yet another variation of a buckle assembly depicted in  FIG. 59 , a clamping member  178  tightens the stability strap  179  to the brace  181 . According to this variation, a second side  185  of the strap  179  is secured to one side of the brace  181 , and a first side  183  of the strap  179  secures to the clamping member  178 . The clamping member  178  is pivotally connected to the brace  181 , and is arranged to be biased against an external surface  187  of the brace  181 . The second side  185  of the strap  179  is detachable from the clamping member  178  and may be secured therewith with a hook and loop fastener system. 
     The buckle assembly may be constructed from plastic or a reinforced composite. A plastic construction provides the sufficient resiliency for the protruding elements to compliantly pass through the receiving holes of the base element. Moreover, the plastic buckle assembly reduces weight of the brace and has some compliancy against the leg of a user of the brace. It is possible to reinforce the buckle assembly with a carbon content, such as a TRIAX based buckle assembly. Other examples of composite based buckle assemblies include those constructed with delron or nylon having reinforcing carbon, KEVLAR or glass fibers. 
     It will be noted that the buckle assembly may also have parts that are constructed from metal, such as an aluminum or titanium alloy. The metal parts provide superior strength and may be sufficiently lightweight. In such a metal based bracket assembly, the protruding elements may be metal components having a resilient o-ring surrounding the protruding elements that has sufficient compressive properties to be placed through the receiving holes of the base portion. Of course, in such an embodiment, the metal protruding parts preferably have a diameter less than the diameter of the receiving holes. 
     Variations of the aforementioned buckle assembly may be used to secure the stability strap to the brace. These variations include an embodiment wherein the strap is fastened to a buckle assembly with a rivet, and a ring is provided on a side of the sleeve opposite the buckle assembly. The length of the strap may be simply adjusted with a hook and loop system provided on the strap. 
     In a variation of the buckle and tightening devices described above, the tightening devices may be secured to a buckle instead of being directly connected to the shells. This permits the buckle to control both ends of the straps. 
     In accordance with one method for donning the knee brace with the inventive buckle assembly, the method is performed in the following steps. First, one force strap is attached to a corresponding buckle assembly, thus requiring only one connection as opposed to two. Next, during an initial fitting, the buckle assembly is connected to the shell and subsequently locked. The leg of the wearer is extended and the force strap is then adjusted such that the force strap is adjustable in length. This results in removing the need to adjust the length of the force strap upon each donning unless the leg changes in size, or for some other reason. The stability strap corresponding to the buckle assembly is also tightened accordingly. Both buckle assemblies are connected to the shells, and the remaining unsecured force straps and stability straps are tightened. 
     Unloading of the knee is conducted with the wearer flexing the knee by bending it, and by tensioning the force strap with corresponding tightening devices. After the wearer is finished with wearing the knee brace, the force strap is released and the buckle assembly is opened. The buckle assembly is then removed from the shells, and the brace is subsequently removed. 
     Upon repeated use, there is no need to adjust the stability straps, and the force straps other than by the tightening device to unload the knee; all of the stability straps and force straps are already configured. Alternatively, a wearer may simply release the tension of the force straps, unbuckle the buckle assembly, and slide the knee brace off of the leg. In either way, the arrangement provides for simple donning of the knee brace onto a leg, and expedites securing and removal of the knee brace. 
     x. Hinge 
     In another feature of the knee brace,  FIG. 60  schematically shows a brace  300  having a hinge  301  in combination with a force strap system of any of the aforementioned embodiments. The hinge  301  extends between frame members  309 ,  311 . The frame members  309 ,  311  include corresponding liners  349 ,  351 , respectively. 
     Preferably, the hinge has flexion and extension stopping features to control hyperextension and anterior drawer of the tibia. The hinge may have an adjustment mechanism that enables a user or clinician to adjust the varus/valgus angle of the hinge. 
     One variation of a hinge  260  for use in the brace of  FIG. 60  is shown in  FIG. 61 . This hinge  260  is generally constructed from plastic or reinforced composite so as to be lightweight and have a generally low profile. The hinge  260  includes flexible brackets  262  that are provided for connecting to the frame members  309 ,  311 . A first end of the proximal and distal arms  264 ,  266  connect to corresponding brackets  262 . A second end of these arms  264 ,  266  defines a head  268 ,  270  having a generally circular gear portion  272 ,  274 . The heads  268 ,  270  are pivotably mounted about axles  276 ,  278  of a housing  280  such that the gear portions  272 ,  274  mesh with one another. 
     Each head  268 ,  270  is provided with first and second stop structures  282 ,  286 . The first stop structures  282  are located on an anterior side of the hinge  260  and are arranged to contact a side surface  284  of the housing  280  in order to limit rotation of the hinge  260  in the anterior direction of the brace. The second stop structures  286  of the head are formed on a generally posterior side of the hinge, and are arranged to limit rotation in the posterior direction of the brace. 
     Apertures  288  may be formed in the housing  280  along the path of the stop structures as the heads  268 ,  270  rotate. These apertures are adapted to receive a screw or pin. The screw or pin is provided to block or engage one of the first and second stop structures to further limit rotation of the hinge. 
     In a variation of the hinge,  FIG. 62  shows a hinge  301  having a different arm construction from the construction of hinge  260 . According to this variation, the arms  303 ,  305  are integrally formed with corresponding heads  315 ,  317 . In addition, each of the arms  303 ,  305  is contoured to accommodate or correspond to the shape of the distal and proximal shells of the knee brace. Gear meshing area  307  exists between heads  315 ,  317 . 
       FIG. 60  shows the hinge  301  connected to proximal and distal shells  309 ,  311  having liners  349 ,  351 , respectively. In this variation, the hinge  301  includes a face plate  319  that covers the heads  315 ,  317 . The arms  303 ,  305  are bent to generally anatomically accommodate a leg. Also, the arms  303 ,  305  are secured to respective shells via pins or buttons  313 . 
     The hinge  301  may be releasably securable to the shells  309  and  311  in  FIG. 60  via the buttons  313 . The buttons  313  are configured to be insertable into the openings  321  and locked in a slotted portion (not shown) that is similar to the slots  445  in the frame  422  of  FIG. 45 , or other frame slots described herein. 
     According to other variations, the removable hinge may be secured to the shells with a series of corresponding snap fasteners, or other suitable fastener devices. The shells may be particularly configured to include apertures that can receive self-piercing fasteners. The removable hinge enables wearers to use the hinge for intense leg activity and greater stability, and remove the hinge for more normal use, greater comfort, and a more streamlined brace. 
     The hinge controls the motion and angular displacement of the brace for stabilization and control of the knee joint. Preferably, the hinge has a thin profile, and is constructed of a lightweight material such as plastic, composite materials, or metals. Unlike other hinges, this hinge does not include an adjustment mechanism since as soon as the force strap system  256  draws the knee against the hinge, the hinge would deflect away from the knee due to its flexibility. 
     Other hinge types may be employed such as those described in U.S. Pat. No. 5,277,698 currently assigned to Generation II USA, Corp. of Bothell, Wash., or in the alternative with a anatomically orthopedic hinge described in U.S. Patent Application Publications 2004/0002674 A1 and 2004/0054311 A1 assigned to Generation II USA, Corp. of Bothell, Wash. This patent and these application publications are incorporated herein by reference. 
     Another embodiment of the knee brace  330  is shown in  FIG. 63  that is configured for stabilizing both medial and lateral sides of the knee. According to this embodiment, force straps  332 ,  334  are configured to extend about opposite sides of the brace  330 . Each of these straps  332 ,  334  connects to frame members  336  that may comprise any of the aforementioned variations discussed herein. 
     In this embodiment, the force straps  332 ,  334  are provided to apply equal pressure on both sides of the knee. Depending on the configuration, one force strap extends along a proximal, lateral side of the knee whereas the other force strap extends along a distal, medial side of the knee. This embodiment is particularly useful for treating ligament injuries or infirmities due to the stability it provides for the knee. 
     A hinge or opposed hinges  340 ,  342 , such as the type of hinges discussed in connection with  FIGS. 61 and 62 , may also be employed to further stabilize the knee with this embodiment. 
     xi. Alternate Knee Brace Embodiment 
       FIG. 64  illustrates another embodiment of a knee brace  210  in accordance with the present invention. This brace  210  includes a proximal frame member  212  and a distal frame member  214  both located on the anterior side of the device  210 , and extending between lateral and medial portions thereof. Both the frame members  212 ,  214  have anterior and posterior facing surfaces. A connecting element  216  connects the frame members  212 ,  214 . A force strap  218  is connected to the frame members  212 ,  214 , and defines first and second strap portions  220 ,  222  that cross at an intersection area  224  located between the frame members  212 ,  214 . 
     The intersection area  224  is generally defined in the same region as in the intersection area in the embodiment of  FIGS. 7-10 . Moreover, the location of the force strap  218  relative to the frame members  212 ,  214  is similar to that also described in connection with the embodiment of  FIGS. 7-10 . 
     A first end of the first strap portion  220  is anchored to the proximal frame member  212  and spirals towards the distal frame member  214 . A plurality of strap guides  226  guide the force strap  218  along an outer surface of the distal member  214  and redirect the force strap  218  towards the proximal member  212 . The second strap portion  222  emerges from the distal member  214  and intersects with the first strap portion  220  while extending towards the proximal member  212 . 
     A second end of the second strap portion  222  is secured to a bracket  228  connected to a cord  230 . The cord  230  is received by a tightening device  232 , of any of the types described herein that are secured to the proximal member  212 . The tightening device  232 , as described in connection with the aforementioned embodiments, is provided to incrementally tension the force strap  218  and selectively allow release of tension in the force strap  218 . The connection between the second strap portion  222  and the tightening device  232  is oriented in a predetermined direction to obtain a preferred orientation at the intersection area  224  between the first and second strap portions  220 ,  222 . 
     Proximal and distal spacers  234 ,  236  are connected to the frame members  212 ,  214 , respectively, along the inner surfaces thereof. As with the aforementioned spacers, the spacers  234 ,  236  have a coating that has a high frictional coefficient against skin or clothing. When applied against skin or clothing, the friction spacers  234 ,  236  resist movement of the knee brace  10  relative to the skin or clothing. 
     The proximal member  212  includes a stability strap  238  secured and extending between opposed lateral and medial sides of the proximal member  212 . The distal member  214  includes a stability strap  240  likewise secured and extending between opposed lateral and medial sides of the distal member  214 . The proximal and distal straps  238 ,  240  preferably have hook and loop fastener systems to connect to the medial and lateral sides of the respective frame members  212 ,  214 . 
     According to the embodiment of  FIG. 64 , the frame members  212 ,  214  may be rigid or flexible members. Moreover, they may be perforated or rendered breathable in the manner described in reference to the shells of  FIGS. 18 and 19 . In variations of the knee brace, however, the frame members may be constructed of soft members that are sufficiently strong to withstand forces on a knee produced by the force strap  218  but sufficiently compliant to provide comfort to a user of the knee brace. 
     The connecting element  216  is a ring that connects to both the proximal and distal members  212 ,  214 . The connecting element  216  is not limited to a ring-like structure, and instead may be provided in any shape having suitable structure and strength that is sufficient to maintain the frame members  212 ,  214  apart while providing sufficient bending over the knee cap during gait. 
     The connecting element is preferably constructed of a medial grade silicone having a sufficient durometer (i.e., 10) and sufficient stiffness to maintain the frame members  212 ,  214  apart. Alternatively, the connecting element  216  may be constructed of a stiff foam from EVA, plastezote or polyurethane. 
     In a variation at least one hinge provided on one of the medial or lateral sides of the brace may take the place of the connecting element, or be provided in combination with the connecting element. 
     The tightening device  232  may include any one of the aforementioned systems used for tightening the force strap  218 . Moreover, the force strap  218  and the stability straps  232  may be mounted onto the shells in any of the aforementioned manners described in connection with the embodiment of  FIGS. 7-10 . 
     xii. Additional Features 
     Additional features may be used in connection with the aforementioned embodiments of the knee brace. 
     One such feature includes load cells that are connected to force straps to measure the force exerted on a knee. According to this feature, load cells are connected to the first and second force straps. These load cells monitor the pressure applied on a knee and relay via connections a pressure reading to the tightening device. The tightening device according to this embodiment, is equipped with a drive motor (not shown) that incrementally adjusts the tightening device by either tightening or releasing the force straps. 
     Of course, this embodiment is not limited to requiring two load cells, and one or multiple load cells may be used to determine the pressure on the knee caused by the force strap. 
     This feature of the tightening device is particularly advantageous since it permits precise tension adjustment of the strap to treat a specific user. The predetermined parameters include a range of dosage requirements for users. These dosage requirements include forces required for a user to unload the compartmental osteoarthritis of the knee. For example, one dosage would equal about 3 Nm of unloading. The maximum unloading, in this example, is 12 Nm so 4 doses would provide a maximum unloading of the knee. The load cells may be configured for a user during a fitting process by an orthotist who could establish a dosage requirement for the user. 
     In another variation, the load cells may be integrated with the knee brace and the tightening device. The data obtained by the load cells can then be used by the tightening device to change the tension in the cross-strap during a gait cycle. According to this variation, an accelerometer device is required to determine the stage of the gait at a particular point in time. This can be particularly useful when walking up or down ramps or hills, or going up or down stairs since the knee is bears weight when in flexion so that the strap is pulled tighter during such stages of walking. 
     In another feature that may be used in combination with embodiments of the knee brace, an inflatable bladder system for providing additional cushioning and fitting of the force straps and stability straps. As illustrated, the force straps are provided with a plurality of bladders connected to pump to provide relief to a leg. The bladders are particularly positioned on the force straps at locations proximal and distal of the leg whereat the force straps apply the maximum pressure on the knee. 
     In operation, the force straps are applied over the knee with slight tension. As the bladders are inflated, the force straps tighten over the knee due to the increase in size of the bladders. The pump permits inflation and deflation of the bladders. The pump may be integrated with the force straps or be located remote therefrom. 
     Examples of pump and bladder systems that may be used in combination with the cross-strap of the knee brace are described in U.S. Pat. Nos. 5,022,109 and 6,598,250 assigned to Dielectrics Industries of Chicopee, Mass., which are incorporated herein by reference. 
     The various embodiments of knee braces described above in accordance with present invention thus provide a product that reduces pain, speeds a healing process, and imparts improved stability to the knee. The knee brace is lightweight and has a streamlined profile that is simple to use for wearers of the brace of various age groups. Moreover, the knee brace permits more precise adjustment of the brace and enables efficient coordination between a medical professional and the wearer as to the degree the knee brace should be configured. Patient comfort is also enhanced, and donning and doffing of the brace is eased with the novel features of the present knee brace. 
     Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. 
     The skilled artisan will recognize the interchangeability of various features from different embodiments. In addition to the variations described herein, other known equivalents for each feature can be mixed and matched by one of ordinary skill in this art to construct a knee brace in accordance with principles of the present invention. 
     Although this invention has been disclosed in the context of certain preferred embodiments and examples, it therefore will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.