Abstract:
A motion controlling hinge for an orthopedic brace is provided. The hinge includes an actuator secured to one arm, and at least one spring member. As the arm with the actuator pivots in a first direction, at a predetermined flexion angle the actuator applies a force to the spring member, causing the spring member to flex. The spring member exerts a force on the actuator tending to bias the actuator away from the spring member, and tending to bias the arm in a second direction opposite the first direction. In a preferred embodiment, the spring member comprises a plurality of flat bar leaf springs. A movable fulcrum enables adjustment of a force exerted by the spring member on the actuator. A variety of differently sized adapters are securable to the actuator. The size of the adapter determines the flexion angle at which the spring member first exerts force on the actuator.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 10/355,486, filed Jan. 30, 2003, currently pending, the entirety of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to orthopedic bracing. More particularly, the present motion controlling hinge for an orthopedic brace provides resistance to joint extension, with the resistance beginning at a predetermined angle and increasing as the joint extends further. 
     2. Description of the Related Art 
     The quadriceps muscles serve as an anterior cruciate ligament (ACL) antagonist that strain the ACL, particularly at smaller knee flexion angles. At knee flexion angles less than 60°, a component of the quadriceps force acts in the anterior direction. Knee structures, primarily the ACL, resist this anterior component. Thus, quadriceps contractions at small flexion angles place strain on the ACL. This strain may be responsible for many ACL injuries. For patients who have recently undergone ACL reconstruction, this strain can cause permanent stretching of the ACL graft, which can in turn create knee instability that could lead to injury of other structures (e.g. meniscus), or to degenerative changes within the joint. In some cases, the patient must undergo a second invasive procedure to reduce the instability. 
     Because of the risk of ACL damage at small flexion angles, physicians commonly recommend avoiding quadriceps contractions at small flexion angles. However, people often have difficulty avoiding small flexion angles during normal activities. Furthermore, movement and activity are important to promoting healing and reducing detrimental effects of ACL reconstruction. Therefore, a knee brace that allows patients to avoid quadriceps contractions at small flexion angles would be of great benefit to ACL reconstruction patients or to people who suffer from ACL deficiencies. 
     One type of knee brace that allows patients to avoid small flexion angles is a brace having extension stops, such that the wearer cannot extend his or her knee past a particular flexion angle. For example, U.S. Pat. No. 4,732,143 to Kausek et al. provides an extension stop removably mountable on a polycentric hinge. The stop limits the forward pivotal rotation of a pair of rigid arms pivotally connected by the hinge. The hinge includes a pair of rigid arms connected at spaced-apart pivotal connections between a pair of parallel face plates. Intermeshing gear teeth on the mating ends of the arms cause simultaneous pivotal action of both arms about their pivotal connections with the plates. The extension stop is a C-shaped plastic body that is attachable along one of the face plates. The stop includes a resilient clip for attaching the stop to one of the face plates. The stop further includes an extension block positionable between the mating ends of the arms to limit the forward rotation of the arms. The extension stop is made of a strong, lightweight plastic. Differently sized block means are provided to allow the user to select the limit of extension. 
     A brace such as the one described in Kausek et al. halts the wearer&#39;s knee extension at a particular flexion angle. A patient wearing such a brace experiences a jarring at maximum extension as the brace comes to a sudden halt. Many patients may find this jarring uncomfortable, and the jarring may cause many patients to fail to comply with the rehabilitation guidelines set by their physicians. A joint brace that provides a cushioned stop at full joint extension and/or full joint flexion can help to reduce or eliminate uncomfortable jarring. The brace might make patients feel safer and more confident, which may lead to better patient compliance with rehabilitation programs and speedier recovery times. 
     Athletes frequently leap off of the ground during various athletic activities. These athletes preferably land with their knees slightly bent. The impact causes their knees to bend further as the quadriceps muscles contract to provide a force that decelerates and eventually halts knee flexion. The knees thus absorb the impact forces and prevent these forces from damaging fragile bones and other joints. 
     Occasionally, however, athletes do not flex their knees while they are in the air. Studies have shown that female athletes tend not to flex their knees as much as male athletes do when landing after a jump. When a person lands with his or her knees fully extended, the knees do not bend. Instead, all of the impact forces are absorbed by the athlete&#39;s bones and/or joints. Such jarring impacts frequently cause injuries. If an athlete were to wear knee braces that included a stop or a cushion that prevented full knee extension, or that biased the knee joint away from full extension, the braces would force the athlete to flex his or her knees while airborne. The athlete would thus always land on flexed knees and would be less likely to injure himself or herself. 
     Several joint braces include hinges that either prevent full joint extension, or provide a cushioned stop at full joint extension. U.S. Pat. No. RE37,209 to Hensley et al. provides an extension deceleration orthosis. The orthosis performs the function of those ligaments that control joint motion, and provides added anteroposterior joint stability. The orthosis comprises a lightweight, external spring assembly, upper and lower elongated arms, and a centric or polycentric fulcrum. The orthosis is adjustable for its range of motion, adaptable for use on many different style orthoses, and includes variable strength to suit corrective, preventive, anthropomorphic, environmental, and usage requirements. The orthosis includes means for mechanically dampening a limb&#39;s angular velocity on extension to prevent hyperextension. The orthosis further includes means for accelerating the limb&#39;s angular velocity on flexion to enable quicker, smoother, less stressful motion. In one embodiment, spring rods are assembled medially and laterally to conventional pairs of elongated orthotic brace arms. The spring rods span the joint fulcrum point by serpentinely engaging roller posts. The assemblage thus decelerates the limb during the last 15 to 20 degrees of extension, preventing the arms from striking a stop, which would create a risk of hyperextension. The assemblage also uses the stored energy of the spring to facilitate limb flexion. 
     U.S. Pat. No. 6,074,355 to Bartlett provides a knee brace having three point fixation and including a pair of first arm members positioned on opposite sides of the knee joint. The lower leg brace member has a pair of second arm members oriented and positionable on opposite sides of the knee joint. The rigid thigh member and lower leg member are secured to the wearer&#39;s leg by means of a flexible strap extending around the back of the leg and adjustably attached thereto. The mating ends of the arms are connected by a pair of parallel spaced-apart face plates forming polycentric hinges that permit the mating ends of the arms to pivot about the connections. Various forms of extension cushions are provided to limit the proximity of the mating ends to one another to thereby limit the forward movement of the arms. 
     None of these braces provides the ability to adjust a magnitude of a force that restrains hinge motion without the necessity of interchanging hinge parts. Further none of these braces provides the advantageous combination of easy adjustability of a magnitude of a force that restrains hinge motion, and easy adjustability of an angle at which the hinge motion controlling force is applied. Therefore, a hinge for an orthopedic brace that provided these advantages would be of great benefit to wearers of orthopedic braces. 
     SUMMARY OF THE INVENTION 
     The preferred embodiments of the motion controlling hinge for orthopedic brace have several features, no single one of which is solely responsible for their desirable attributes. Without limiting the scope of this invention as expressed by the claims that follow, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description of the Preferred Embodiments,” one will understand how the features of the preferred embodiments provide advantages, which include easy adjustability of a magnitude of a force that restrains hinge motion, and easy adjustability of an angle at which the hinge motion controlling force is applied. 
     A preferred embodiment of the hinge for orthopedic brace comprises a hinge plate, a spring member, and first and second arms pivotably secured to the hinge plate. An actuator is secured to the second arm. As the arms pivot in a first direction such that an angle between them increases, once the arms reach a desired extension angle, the spring member exerts a force on the actuator tending to bias the second arm in a second direction opposite the first direction. 
     Another preferred embodiment of the hinge for orthopedic brace comprises an orthopedic brace including a hinge. The hinge comprises a hinge plate, a spring member and first and second arms pivotably secured to the hinge plate. An actuator is secured to the second arm. As the brace pivots toward full extension, the spring member exerts a force on the actuator tending to bias the brace away from full extension. 
     Another preferred embodiment of the hinge for orthopedic brace comprises a hinge plate, a leaf spring, and first and second arms pivotably secured to the hinge plate. An actuator is secured to the second arm. As the second arm pivots in a first direction, the actuator contacts the leaf spring, causing the leaf spring to flex such that the leaf spring exerts a force on the actuator tending to bias the actuator away from the leaf spring, and tending to bias the second arm in a second direction opposite the first direction. 
     Another preferred embodiment of the hinge for orthopedic brace comprises a hinge plate, a leaf spring shaped substantially as a flat bar, and first and second arms pivotably secured to the hinge plate. As the arms pivot toward a first configuration in which an angle between them approaches 180°, the leaf spring exerts a force on the second arm tending to bias the second arm away from the first configuration. 
     Another preferred embodiment of the hinge for orthopedic brace comprises a resistance member for providing resistance to motion of the hinge in a first direction within a predetermined range of motion of the hinge, and an adjustment member adapted to apply a force on the resistance member for adjusting an amount of the resistance provided by the resistance member. When the adjustment member is located in a first location relative to the resistance member, the resistance provided by the resistance member has a first magnitude. When the adjustment member is located in a second location relative to the resistance member, the resistance provided by the resistance member has a second magnitude that is different from the first magnitude. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiments of the motion controlling hinge for orthopedic brace, illustrating its features, will now be discussed in detail. These embodiments depict the novel and non-obvious hinge shown in the accompanying drawings, which are for illustrative purposes only. These drawings include the following figures, in which like numerals indicate like parts: 
         FIG. 1  is a top-rear perspective view of a preferred embodiment of the motion controlling hinge for orthopedic brace according to the present invention; 
         FIG. 2  is a bottom-rear perspective view of the hinge of  FIG. 1 ; 
         FIG. 3  is an exploded top-rear perspective view of the hinge of  FIG. 1 ; 
         FIG. 4  is a partially exploded top-rear perspective view of the actuator, adapter, bumper, springs, fulcrum, arms and outer hinge plate of the hinge of  FIG. 1 ; 
         FIG. 5  is a top plan view of the actuator, adapter, bumper, springs, fulcrum, arms and friction plate of the hinge of  FIG. 1 , illustrating the configuration of these components when the arms are positioned such that the adapter contacts the bumper and the springs are undeflected; 
         FIG. 6  is a top plan view of the springs of the hinge of  FIG. 1 , illustrating, schematically, the bending load applied to the springs by the hinge components; 
         FIG. 7  is a top plan view of the components of  FIG. 5 , illustrating the configuration of these components when the arms are positioned at full extension, such that the springs are fully deflected, and the fulcrum is located at a maximum distance from the bumper; 
         FIG. 8  is a top plan view of the components of  FIG. 5 , illustrating the configuration of these components when the arms are positioned at full extension, such that the springs are fully deflected, and the fulcrum is located at a minimum distance from the bumper; 
         FIG. 9  is a bottom-rear perspective view of the actuator, adapter, bumper, springs and outer hinge plate of the hinge of  FIG. 1 ; 
         FIG. 10  is a bottom plan view of the actuator, adapter, bumper, springs, fulcrum and outer hinge plate of the hinge of  FIG. 1 , illustrating the configuration of these components when the arms are positioned such that the adapter contacts the bumper and the springs are undeflected; 
         FIG. 11  is a bottom plan view of the actuator, adapter, bumper, springs, fulcrum and outer hinge plate of the hinge of  FIG. 1 , illustrating the configuration of these components when the arms are positioned at full extension, such that the springs are fully deflected, and the fulcrum is located at a maximum distance from the bumper; 
         FIGS. 12-14  are top plan views of the actuator, adapter, bumper, springs, fulcrum, arms and friction plate of the hinge of  FIG. 1 , illustrating adapters of different sizes, and the relative configurations of these components when the arms are positioned such that the adapter contacts the bumper and the springs are undeflected; 
         FIG. 15  is a top plan view of the hinge of  FIG. 1 , illustrating the easy accessibility of the adapter with the cosmetic cover removed; and 
         FIG. 16  is a top-rear perspective view of the actuator, adapter, bumper, springs and arms of the hinge of  FIG. 1 , illustrating the screw that is preferably used to hold the adapter in place on the second arm. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  illustrate the exterior of the present motion controlling hinge  20  for orthopedic brace.  FIG. 3  illustrates, in an exploded view, the interior components of the hinge  20 . The hinge  20  comprises a first rigid arm  22  and a second rigid arm  24  pivotably secured between an inner hinge plate  26  ( FIGS. 2 and 3 ) and an outer hinge plate  28  ( FIGS. 1 and 3 ). With reference to  FIGS. 3 and 4 , each hinge plate  26 ,  28  preferably includes a first pivot aperture  30  and a second pivot aperture  32  spaced from the first pivot aperture  30 . Each arm  22 ,  24  preferably includes a pivot aperture  34  near a mating end thereof. As shown in  FIGS. 2 and 3 , a first fastening member  36 , such as a rivet, passes through the first pivot aperture  30  on each hinge plate  26 ,  28  and through the pivot aperture  34  on the first arm  22 , thereby pivotably securing the first arm  22  between the hinge plates  26 ,  28 . A second fastening member  36 , such as a rivet, passes through the second pivot aperture  32  on each hinge plate  26 ,  28  and through the pivot aperture  34  on the second arm  24 , thereby pivotably securing the second arm  24  between the hinge plates  26 ,  28 . 
     In the illustrated embodiment, the pivot aperture  34  on each arm contains a reinforcing insert  38  ( FIG. 4 ). Preferably, the arms  22 ,  24  are constructed of a relatively inexpensive and lightweight metal, such as aluminum. Such a lightweight metal lowers the overall weight of a brace including the present hinge  20 , making the brace more comfortable for the wearer. However, lightweight metals typically do not have sufficient hardness to enable the arms  22 ,  24  to withstand prolonged use in the present hinge  20 . At the pivot apertures  34  in the arms  22 ,  24 , the arms  22 ,  24  rub against the fastening members  36 . Similarly, a first gear tooth  40  ( FIG. 4 ) on each arm  22 ,  24  rubs against gear teeth on the opposite arm  22 ,  24 . Friction at these contact points tends to wear down the material at the pivot apertures  34  and the first gear teeth  40 . Therefore, the reinforcing inserts  38  provide the arms  22 ,  24  with greater hardness at the points where the arms  22 ,  24  experience the greatest wear and tear. Those of skill in the art will appreciate that the reinforcing inserts  38  are not necessary to achieve the advantages of the present hinge  20 . The reinforcing inserts  38  merely prolong the expected life span of the present hinge  20  while maintaining low weight and low cost. 
     With reference to  FIG. 16 , the inserts  38  include a ring-shaped portion  42  with an elongate radial protrusion  44 . Opposite the radial protrusion  44 , the ring-shaped portion  42  includes first and second arcuate protrusions  46  that are substantially tangential to the ring-shaped portion  42 . The mating end of each arm  22 ,  24  preferably includes a cut-out portion having a shape complementary to that of the inserts  38 . The inserts  38  may be retained within the cut-out portions by any appropriate means, such as a friction fit or an adhesive. An end of the radial protrusion  44  opposite the ring-shaped portion  44  comprises a first gear tooth  40 . The operation of the geared ends of the arms  22 ,  24  is described in detail below. The inserts  38  are preferably constructed of a material having a high hardness, such as stainless steel. The inserts  38  thus are better able to withstand the wear and tear that the softer arms  22 ,  24  experience at the pivot apertures  34  and the first gear tooth  40 . 
     The hinge  20  may include a first friction-reducing plate  46  ( FIG. 3 ) sandwiched between the outer hinge plate  28  and the arms  22 ,  24 . The hinge  20  may also include a second friction-reducing plate  48  sandwiched between the inner hinge plate  26  and the arms  22 ,  24 . The friction-reducing plates  46 ,  48  are preferably constructed of a low-friction material, such as a plastic, TEFLON® or DELRIN®. The friction-reducing plates  46 ,  48  enable the arms  22 ,  24  to pivot more easily with respect to the hinge plates  26 ,  28 . Those of skill in the art will appreciate that the hinge  20  need not include the friction-reducing plates  46 ,  48 . 
     An outer surface  50  of the outer hinge plate  28  preferably includes a removable cosmetic cover  52  ( FIGS. 1 and 3 ) that enhances the outward appearance of the hinge  20 . The cover  52  may be secured to the outer hinge plate  28  with, for example, adhesive or an interlocking “snap-fit” engagement. The cover  52  hides from view the pivot apertures  30 ,  32  and an adapter access opening  54 , which is described in detail below. 
     As shown in  FIGS. 3 and 4 , an outer surface  56  of the second arm  24  preferably includes an actuator  58  adjacent the pivot aperture  34 . In the illustrated embodiment, the actuator  58  comprises an irregularly shaped solid. The actuator  58  includes first and second through-holes  60  ( FIG. 4 ). The first and second through-holes  60  on the actuator  58  align with first and second through-holes  62  ( FIG. 3 ) in the second arm  24 . Fastening members  64  ( FIG. 3 ), such as screws or rivets, cooperate with the first and second through-holes  62  in the second arm  24 , and with the first and second through-holes  60  in the actuator  58 , to secure the actuator  58  to the second arm  24 . Those of skill in the art will appreciate that the actuator  58  need not be secured to the second arm  24  with fastening members. For example, the actuator  58  could be bonded to the second arm  24  with adhesive, or it could be welded to the second arm  24 . Alternatively, the actuator  58  could be formed integrally with the second arm  24 , such as by die-casting. If the actuator  58  is secured to the second arm  24  with fastening members  64 , as shown, preferably the inner hinge plate  26  includes a cut-out portion  112  ( FIG. 2 ) so that heads of the fastening members  64  do not interfere with the inner hinge plate  26 . 
     The actuator  58  is preferably constructed of a hard durable material, such as a metal. A preferred metal is stainless steel. An adapter  66  is selectively securable to the actuator  58 , as shown in  FIGS. 4 ,  5  and  16 . The adapter  66  is substantially J-shaped in top plan aspect ( FIG. 5 ), and includes an interior curved surface  68  that is complementary to an outer side portion  70  of the actuator  58 . The adapter  66  thus fits snugly around the actuator  58 . The hooked portion  72  of the adapter  66  includes a crescent-shaped flange having a semi-cylindrical concave edge  74 . A retaining member  76 , such as a screw, engages a third aperture  78  ( FIG. 3 ) in the second arm  24 , such that a longitudinal axis of the retaining member  76  is substantially coextensive with a longitudinal axis of the flange concave edge  74 . A cylindrical exterior of the retaining member  76  thus cooperates with the concave edge  74  of the flange, thereby firmly holding the adapter  66  in place on the actuator  58 . 
     The adapter  66  is preferably constructed of a hard durable material, such as a metal. A preferred metal is stainless steel. As described below, the adapter  66  enables easy adjustment of a joint flexion angle at which resistance to further flexion begins. 
     An interior of the outer hinge plate  28  ( FIG. 9 ) houses a plurality of leaf springs  80 . In the illustrated embodiment, each leaf spring  80  comprises a flat bar of resilient material. Those of skill in the art will appreciate that the leaf springs  80  need not be shaped as flat bars. For example, the leaf springs  80  could be wedge-shaped (straight tapered bars), or the leaf springs  80  could be arcuate. An upper edge  81  ( FIG. 4 ) of each leaf spring  80  includes a ridge  83  near a first end  82  thereof. A portion (not shown) of the outer hinge plate  28  has a shape that is complementary to the shape of the ridges  83 . The ridges  83  nest within this portion of the outer hinge plate  28 , and prevent the leaf springs  80  from translating along an axis A ( FIGS. 9 and 10 ) upon which both hinge plate pivot apertures  30 ,  32  lie. 
     The leaf springs  80  are preferably constructed of a resilient material that returns to its original shape after the removal of an applied load. A preferred material for the leaf springs  80  is stainless steel. However, those of skill in the art will appreciate that the leaf springs  80  could be constructed of other materials in order to alter the stiffness of the leaf springs  80 . For example, less rigid metals or plastics could be used to provide more flexible leaf springs  80 , and more rigid metals could be used to provide more stiff leaf springs  80 . 
     In the illustrated embodiment, three leaf springs  80  are provided, and the leaf springs  80  are freely slidable with respect to one another except in the vicinity of the ridges  83 . In this vicinity, the nesting of the ridges  83  within the outer hinge plate  28  prevents the leaf springs  80  from sliding with respect to one another. The illustrated leaf springs  80  are of unequal lengths. The innermost leaf spring  80  (the leaf spring  80  that lies closest to the pivot apertures  30 ,  32 ) is the longest, and the outermost leaf spring  80  the shortest. This configuration allows the springs  80  greater freedom to flex without interfering with the walls of the outer hinge plate  28 . Those of skill in the art will appreciate that the leaf springs  80  need not have unequal lengths. 
     The three leaf spring configuration provides the advantageous combination of a high amount of extension resistance without significant risk that the leaf springs  80  will break. If the three leaf springs  80  are replaced by a single solid leaf spring  80  having the same stiffness as the three illustrated leaf springs  80 , the single leaf spring  80  will be much more likely to break. Nevertheless, those of skill in the art will appreciate that the three leaf springs  80  could be replaced by more or fewer leaf springs  80 , including a single leaf spring  80 , in order to suit a particular application. Those of skill in the art will also appreciate that the shape, dimensions and/or composition of each leaf spring  80  could be varied to provide desired extension resistance characteristics for the hinge  20 . For example, if greater extension resistance is desired, some or all of the leaf springs  80  could be made of a stiffer material. Alternatively, one leaf spring  80  having the same thickness as the three combined leaf springs  80  could be provided. Alternatively, the three springs could be adhered to one another so that they behave essentially as a unitary leaf spring  80 . 
     With reference to  FIGS. 9 and 10 , the first end  82  of each leaf spring  80  is constrained by a first wall  84  of the outer hinge plate  28  against translation toward the axis A. A second wall  86  of the outer hinge plate  28  constrains each leaf spring  80 , at a point adjacent the first end  82  of each, against translation away from the axis A. Second ends  88  of the leaf springs  80  are free to translate away from the axis A. The leaf springs  80  are thus analogous to cantilevered beams. 
     The outer hinge plate  28  houses a bumper  90 , which is substantially L-shaped in plan aspect ( FIG. 10 ). The bumper  90  is preferably constructed of a deformable but resilient material that provides some cushioning. Preferred materials for the bumper  90  include urethane, rubber and plastic. The bumper  90  provides a cushion between the adapter  66  and the leaf springs  80 , which reduces any sound made when the adapter  66  contacts the leaf springs  80 , as described below. Those of skill in the art will appreciate that the bumper  90  is not necessary to achieve the advantages of the present hinge  20 . The adapter  66  may contact the leaf springs  80  directly. Alternatively, if the adapter  66  were removed completely, the actuator  58  may contact the leaf springs  80  directly. 
     An upright portion  92  of the bumper  90  includes a flat indentation  94  adjacent an interior corner where the upright portion  92  meets the base portion  96  of the bumper  90 . The flat indentation  94  receives a post  98  ( FIG. 9 ) that protrudes from the outer hinge plate  28 . The post  98  retains the bumper  90  in its rest position, and guides the bumper  90  back to the rest position, as described below. 
     The outer hinge plate  28  includes a plurality of apertures  100  adjacent a front edge  102  thereof. In the illustrated embodiment, three apertures  100  are provided, and all the apertures  100  include internal threads. Those of skill in the art will appreciate that more or fewer apertures  100  could be provided to suit a particular application, and that the apertures  100  need not be threaded. A longitudinal axis of each aperture is substantially perpendicular to a plane defined by the outer hinge plate  28 . When viewed in plan aspect ( FIG. 15 ), centers of the apertures  100  are collinear. 
     The apertures  100  are adapted to receive a fulcrum  104 , which in the illustrated embodiment comprises a shaft with an externally threaded head portion ( FIG. 3 ). The head portion preferably includes a surface feature  106 , such as a hexagonal depression, that is adapted to engage an adjustment tool, such as a hex key. The threaded portion of the fulcrum  104  engages the threads in one of the apertures  100  to secure the fulcrum  104  within that aperture, as shown in  FIGS. 1 and 15 . Thus, the fulcrum  104  is selectively positionable within one of the three apertures  100 . When the fulcrum  104  is disposed in one of the apertures  100 , the non-threaded portion of the shaft abuts the outermost leaf spring  80 , as shown in  FIG. 4 . The position of the fulcrum  104  thus determines the bending characteristics of the leaf springs  80 , as described below. 
     Those of skill in the art will appreciate that the fulcrum  104  could be retained within one of the apertures  100  using means other than a threaded engagement. For example, a friction fit could retain the fulcrum  104  within one of the apertures  100 . However, a threaded engagement provides a wearer of a brace including the present hinge  20  with the advantageous ability to quickly remove the fulcrum  104  from a first aperture  100  and replace it in a different aperture  100 . Thus, without disassembling the hinge, and without interchanging any parts of the hinge  20 , the wearer can adjust the bending characteristics of the leaf springs  80 , and thereby adjust a magnitude of the extension resistance felt by the wearer. 
     The mating end of each arm  22 ,  24  includes a first gear tooth  40  ( FIG. 4 ) and additional gear teeth  108  ( FIG. 3 ). The teeth  40 ,  108  on the first arm  22  interlock with the teeth  40 ,  108  on the second arm  24 , such that the arms  22 ,  24  cannot pivot independently. As described above, the radial protrusion  44  from each reinforcing insert  38  comprises the first gear tooth  40  on each arm  22 ,  24 . The harder material of the insert  38  reduces the amount of wear that the first gear teeth  40  experience, increasing the life span of the present hinge  20 . 
     As the arms  22 ,  24  pivot, the actuator  58  and adapter  66  move with the second arm  24 . The arms  22 ,  24  are freely pivotable from a full flexion configuration (not shown) to a flexion angle at which the adapter  66  first contacts the bumper  90  ( FIG. 5 ). As the arms  22 ,  24  pivot farther toward full extension ( FIG. 7 ), the adapter  66  applies a force to the bumper  90 , compressing the bumper  90  between the adapter  66  and the leaf springs  80 . As the bumper  90  compresses, it in turn applies a force to the leaf springs  80 , flexing the leaf springs  80  a small amount. Eventually, the bumper  90  compresses enough to allow the adapter  66  to contact the leaf springs  80 , as shown in  FIG. 7 . The bumper  90  thus reduces any noise made when the adapter  66  contacts the leaf springs  80 , because the leaf springs  80  are already flexing when the adapter  66  contacts the leaf springs  80 . The adapter  66  and the bumper  90  then simultaneously apply force to the leaf springs  80 , flexing the leaf springs  80  farther until they contact the wall  110  ( FIGS. 9 and 10 ) of the outer hinge plate  28 . In the illustrated embodiment, the hinge  20  reaches full extension as the leaf springs  80  contact the wall  110 . Those of skill in the art will appreciate, however, that the leaf springs  80  may contact the wall  110  at any flexion angle. 
     The hinge assembly  20  thus places the leaf springs  80  in a three-point bending load, as illustrated in  FIG. 6 . The actuator  58 /bumper  90  assembly applies a load A to the free ends  88  of the leaf springs  80  in a direction away from the axis A. The outer hinge plate first wall  84  ( FIGS. 9 and 10 ) applies a load W to the fixed end  82  of the leaf springs  80  in a direction away from the axis A. The outer hinge plate second wall  86  or fulcrum  104  applies a load F to an intermediate portion of the leaf springs  80  in a direction toward the axis A. The location of the load F depends upon the position of the fulcrum  104 , if the fulcrum  104  is inserted in one of the apertures  100 . If the fulcrum  104  is absent, the outer hinge plate second wall  86  applies the force F. 
     The leaf springs  80  deflect as shown in  FIG. 7  under the bending load. As the leaf springs  80  deflect from the configuration of  FIG. 5  to that of  FIG. 7 , the force necessary to deflect the springs an incremental amount increases. Thus, a person wearing a knee brace including the hinge  20  experiences a steadily increasing resistive force as he or she extends his or her knee farther and farther. The hinge  20  thus provides a cushioned stop at full extension, and eliminates the uncomfortable jarring that could cause the problems outlined above. 
     When the wearer relaxes his or her leg, the leaf springs  80  urge the knee to flex until the leaf springs  80  return to their straight configuration, which is shown in  FIGS. 5 and 10 . As the hinge components move in this direction, the post  98  ( FIG. 9 ) on the interior of the outer hinge plate  28  engages the base portion  96  of the bumper  90  and guides the bumper  90  back to its rest position, as shown in  FIGS. 10 and 11 . 
     The multiple positions for the fulcrum  104 , and the removability of the fulcrum  104 , enable the wearer, or a physician treating the wearer, to quickly adjust an amount of extension resistance experienced by the wearer without disassembling the hinge and without interchanging any parts of the hinge  20 . With reference to  FIG. 6 , the properties of the leaf springs  80  can be determined using the well known model of a simply supported beam with an overhanging load. The deflection at the leaf spring free ends  88  is given by the following equation: 
     
       
         
           
             
               y 
               FA 
             
             = 
             
               
                 
                   A 
                   ⁡ 
                   
                     ( 
                     
                       x 
                       - 
                       l 
                     
                     ) 
                   
                 
                 
                   6 
                   ⁢ 
                   EI 
                 
               
               ⁡ 
               
                 [ 
                 
                   
                     
                       ( 
                       
                         x 
                         - 
                         l 
                       
                       ) 
                     
                     2 
                   
                   - 
                   
                     a 
                     ⁡ 
                     
                       ( 
                       
                         
                           3 
                           ⁢ 
                           x 
                         
                         - 
                         l 
                       
                       ) 
                     
                   
                 
                 ] 
               
             
           
         
       
     
     where 
     y FA =deflection of the leaf springs  80  at any point between the applied load A and the reaction force F; 
     A=magnitude of the load applied by the actuator  58 /adapter  66  to the leaf springs  80 ; 
     x=distance from the leaf spring fixed ends  82 , as measured along the x-axis; 
     l=distance between the leaf spring fixed ends  82  and reaction force F applied by the hinge plate second wall  86  or fulcrum  104 , as measured along the x-axis; 
     a=distance between the reaction force F applied by the hinge plate second wall  86  or fulcrum  104  and the load A applied by the actuator  58 /adapter  66  to the leaf springs  80 , as measured along the x-axis; 
     E=modulus of elasticity of the leaf springs  80  (a constant determined by the material used to construct the leaf springs  80 ); and 
     I=moment of inertia of the leaf springs  80  (a constant determined by the cross-sectional shape of the leaf springs  80 ). 
     To determine the deflection at the leaf spring free ends  88  (which is closely approximated by the deflection at the point of application of the applied load A), substitute (a+l) for x in the equation above. The equation then simplifies to: 
     
       
         
           
             
               y 
               FA 
             
             = 
             
               
                 
                   - 
                   
                     Aa 
                     2 
                   
                 
                 
                   3 
                   ⁢ 
                   EI 
                 
               
               ⁢ 
               
                 ( 
                 
                   a 
                   + 
                   l 
                 
                 ) 
               
             
           
         
       
     
     This equation illustrates that the deflection at the leaf spring free ends  88  is directly dependent upon both the magnitude of the load A applied by the actuator  58 /adapter  66  to the leaf springs  80 , and the distance a, which is the distance between the reaction force F applied by the hinge plate second wall  86  or fulcrum  104  and the applied load A. As one of these variables decreases, the other must increase in order to maintain a constant deflection of the leaf spring free ends  88 . Thus, as the fulcrum  104  is moved toward the leaf spring free ends  88 , thus decreasing the distance a, the applied load A must increase in order to maintain a constant deflection. In order for a wearer of a brace including the hinge  20  to extend his or her knee to a given flexion/extension angle, he or she will have to apply a greater force A as the fulcrum  104  moves toward the leaf spring free ends  88 . In other words, the wearer experiences increasing extension resistance as the fulcrum  104  moves toward the leaf spring free ends  88 . In a preferred embodiment, the hinge  20  provides a maximum of 14 in.-lbs. of resistance when the fulcrum  104  is located in the aperture  100  farthest from the leaf spring free ends  88 , a maximum of 28 in.-lbs. of resistance when the fulcrum  104  is located in the intermediate aperture  100 , and a maximum of 42 in.-lbs. of resistance when the fulcrum  104  is located in the aperture  100  closest to the leaf spring free ends  88 . 
     With the fulcrum  104  removed (not shown), the wearer experiences very light extension resistance. With the fulcrum  104  positioned in the aperture  100  located a maximum distance from the free ends  88  of the leaf springs  80 , as illustrated in  FIGS. 5 and 7 , the wearer experiences light extension resistance. With the fulcrum  104  positioned in the intermediate aperture  100 , the wearer experiences an intermediate amount of extension resistance. With the fulcrum  104  positioned in the aperture  100  located a minimum distance from the free ends  88  of the leaf springs  80 , as illustrated in  FIG. 8 , the wearer experiences heavy extension resistance. Those of skill in the art will appreciate that more apertures  100  could be provided in order to enable finer adjustment of the amount of extension resistance provided by the hinge  20 . Those of skill in the art will further appreciate that the fulcrum  104  could be positionable along the leaf springs  80  using alternate apparatus. For example, the fulcrum  104  could comprise a portion of a switch (not shown) that is slidable along the outer hinge plate  28  and capable of being locked in place at a plurality of positions along the leaf springs  80 . 
     The design of the present hinge  20  facilitates rapid removal and adjustment of the position of the fulcrum  104 . As described above, the fulcrum  104  is alternately positionable in one of a plurality of apertures  100  in the outer hinge plate  28 . To secure the fulcrum  104  within one of the apertures  100 , the wearer inserts  38  the unthreaded shaft portion of the fulcrum  104  into one of the apertures  100  until the threads on the fulcrum  104  engage the threads within the aperture  100 . Using an adjustment tool, such as a hex key, the wearer then rotates the fulcrum  104  within the aperture  100  until the fulcrum  104  is inserted a sufficient amount that it will not pop out of the aperture  100  during normal use of the hinge  20 . Preferably, the wearer continues rotating the fulcrum  104  until it no longer protrudes from the outer surface  50  of the outer hinge plate  28 . To move the fulcrum  104  to a different aperture  100 , the wearer uses the adjustment tool to rotate the fulcrum  104  in the opposite direction, so that it withdraws from the aperture  100 . The wearer then moves the fulcrum  104  to the desired aperture  100 , and performs the insertion process just described. 
     The ability to quickly and easily move the fulcrum  104  from one aperture  100  to another enhances the versatility of a brace including the present hinge  20 . For example, people of all different sizes and strengths may wear a brace including the present hinge  20 . Wearers of great strength would likely benefit most from a brace having heavy extension resistance, while those of lesser strength would likely benefit most from a brace having light extension resistance. No matter the size and strength of the wearer, however, the present hinge  20  is quickly and easily adjustable to accommodate virtually any wearer. And the adjustment procedure does not require the wearer to disassemble the hinge or interchange any parts. Further, certain wearers may benefit from light extension resistance during an early phase of therapy, with the extension resistance steadily increasing as therapy progresses. Other wearers may benefit from heavy extension resistance during an early phase of therapy, with the extension resistance steadily decreasing as therapy progresses. The present hinge  20  enables such patients to undergo a course of therapy without having to change braces as therapy progresses. 
     The hinge  20  enables easy adjustment of the flexion angle at which the wearer first experiences extension resistance. As shown in  FIGS. 12-14 , the wearer may place adapters  66  of various sizes on the actuator  58 . In  FIG. 12 , a relatively small adapter  66  is positioned on the actuator  58 . The adapter  66  first contacts the bumper  90  at a flexion angle of approximately 35°, and the wearer first experiences extension resistance at this same angle. In  FIG. 13 , a slightly larger adapter  66  is positioned on the actuator  58 . The adapter  66  first contacts the bumper  90  at a flexion angle of approximately 45°, and the wearer first experiences extension resistance at this same angle. Finally, in  FIG. 14 , an even larger adapter  66  is positioned on the actuator  58 . The adapter  66  first contacts the bumper  90  at a flexion angle of approximately 55°, and the wearer first experiences extension resistance at this same angle. Those of skill in the art will appreciate that adapters  66  of virtually any size may be positioned on the actuator  58  so that the wearer first experiences extension resistance at virtually any flexion angle. Those of skill in the art will appreciate that the adapter  66  could be completely removed in order to further decrease the flexion angle at which the wearer first experiences extension resistance. 
     As described above, the adapter  66  is secured in place with the retaining member  76  ( FIGS. 15 and 16 ). To exchange one adapter  66  for another of a different size, the wearer first removes the cosmetic cover  52 , if one is provided, from the outer hinge plate  28 . The wearer can then access the adapter  66  through the adapter access opening  54  in the outer hinge plate  28 . The wearer removes the retaining member  76  using an appropriate tool, such as a screwdriver or a hex key. The wearer can then remove the adapter  66  from the actuator  58  using his or her fingers or a tweezers, and replace the adapter  66  with one of a different size. To secure the adapter  66  in place, the wearer replaces the retaining member  76 . Finally, the wearer replaces the cosmetic cover  52 , if one is provided. 
     The present hinge  20  has been described above as a hinge for providing resistance to joint extension. Those of skill in the art will appreciate that the configuration of the present hinge  20  could easily be adapted to enable the hinge  20  to provide resistance to joint flexion. For example, if the leaf springs  80  were housed within the outer hinge plate  28  such that they were lay adjacent a rear edge of the outer hinge plate  28 , then the actuator  58 /adapter  66  assembly would approach and contact the leaf springs  80  as a flexion angle between the arms  22 ,  24  increased. 
     The present hinge  20  has also primarily been described above as a hinge for use with a knee brace. Those of skill in the art will appreciate that the present hinge  20  is adapted for use in a brace that is worn about any body joint. 
     SCOPE OF THE INVENTION 
     The above presents a description of the best mode contemplated for carrying out the present motion controlling hinge for orthopedic brace, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains to make and use this hinge. This hinge is, however, susceptible to modifications and alternate constructions from that discussed above that are fully equivalent. Consequently, this hinge is not limited to the particular embodiments disclosed. On the contrary, this hinge covers all modifications and alternate constructions coming within the spirit and scope of the hinge as generally expressed by the following claims, which particularly point out and distinctly claim the subject matter of the hinge.