Abstract:
An orthopaedic knee brace comprising an upper arm and a lower arm securable to a wearer&#39;s leg above and below the knee joint. There is a pivotable joint at the ends of the arms to allow flexing of the knee by pivoting movement of the arms. A locking mechanism is provided to control pivoting of the joint to lock one of the upper or lower arms relative to the joint while automatically unlocking the other arm to permit pivoting movement of the other arm about the joint. The joint and locking mechanism co-operate to form a light weight structure that operates smoothly to imitate the complex bending motion of the knee while supporting the knee.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to joints for orthopaedic braces and more particularly to a mechanical joint for a knee brace incorporating a locking mechanism to control and co-ordinate movement of the joint. 
     BACKGROUND OF THE INVENTION 
     The human knee is not a simple hinge joint. The knee is capable of gliding, rocking and rotational movement that make it difficult to imitate in a simple mechanical joint. When the knee bends and straightens during walking or running, the femur and tibia interact in sliding, gliding and rotational movement relative to one another. It is only when the leg is straightened and supporting the weight of the body that the knee joint is locked. Thus, the natural knee joint has a point of pivot that moves about as the leg is bent and straightened with the knee providing a restricted universal action unless firmly locked as described. 
     When bracing the knee, it is generally desirable that the supported knee be allowed to operate in as natural a manner as possible so as not to impart abnormal forces across the joint during activity and to allow the wearer to bend and straighten the leg in a normal manner. 
     A leg brace requires a mechanical joint that will support the knee and reproduce as closely as possible the complex pivoting motion of the knee. At the same time, the mechanical joint must not be so heavy, bulky or complex that the normal movement of the knee is impeded. Various mechanical joints have been developed to satisfy the above requirements. 
     U.S. Pat. No. 3,902,482 issued Sep. 2, 1975 teaches an orthopaedic brace having a mechanical joint interconnecting brace arms that attach to the legs of the wearer above and below the knee. The joint is lightweight, relatively simple in construction and does a good job of imitating the motion of the knee. This same joint has been used in other patented braces or bracing methods such as U.S. Pat. No. 5,277,698 issued Aug. 18, 1993, U.S. Pat. No. 5,302,169 issued Apr. 12, 1994 and U.S. Pat. No. 5,562,605 issued Oct. 8, 1996. All these patents and the present invention are commonly owned. 
     While the mechanical joint disclosed in the above references does a good job of reproducing the natural motion of the human knee joint, the joint suffers from the drawback that it permits knee joint movement that is not natural at certain positions of the mechanical joint. For example, when the knee is straightened and locked, the lower leg should not be able to pivot. In flexion, the two halves of the joint tend to loosen relative to each other in the anterior/posterior plane which is clearly undesirable for a knee brace intended to support and guide the knee. To address this problem, the knee brace hinge was modified to include an elastic link extending between the lower arm and the joint that tends to resist movement of the lower arm when the knee is locked. This is an imperfect solution as resistance to movement of the lower arm is also present when movement of the lower arm is desired. 
     SUMMARY OF THE INVENTION 
     Accordingly, there is a need for a knee brace and mechanical joint that accurately mimics the complex movement of the human knee joint and at the same time does a complete job of bracing and supporting the knee over the full range of motion of the knee. In some positions, this involves locking one or the other of the brace arms from movement depending on the extent of flexing of the knee. 
     The present invention provides an orthopaedic knee brace that incorporates a locking mechanism that automatically locks one of the brace arms while unlocking the other arm to more accurately imitate the motion of the human knee and offer better bracing and support for the knee. 
     Therefore, the present invention provides in an orthopaedic knee brace comprising an upper arm and a lower arm securable to a wearer&#39;s leg on opposite sides of the knee joint and a pivotable joint at the ends of the arms to allow pivoting of the knee by pivoting movement of the arms, the improvement comprising: 
     a locking mechanism to control pivoting of the joint to lock one of the upper or lower arms relative to the joint while automatically unlocking the other arm to permit pivoting movement of the other arm about the joint. 
     The brace of the present invention with its joint and locking mechanism provides a lightweight, reliable structure that is able to smoothly pivot to imitate the complex motion of the knee while fully supporting the knee. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Aspects of the present invention are illustrated, merely by way of example, in the accompanying drawings in which: 
     FIG. 1 is a front view showing a preferred embodiment of the brace of the present invention in position on the leg of a wearer; 
     FIG. 2 is a front view of the brace according to the invention; 
     FIG. 3 is a side elevation view through the brace with some portions in cross-section; 
     FIG. 4 is an exploded view showing the component parts of a preferred embodiment of the present invention; 
     FIG. 5 is a detail section view through the brace joint that shows the position of the rocker arm of the locking mechanism to lock the lower arm and permit free pivoting of the upper arm; 
     FIG. 5 a  is a front schematic view of the brace corresponding to the position shown in FIG. 5; 
     FIG. 6 is a detail section view through the brace joint that shows the position of the rocker arm of the locking mechanism to lock the upper arm and permit free pivoting of the lower arm; and 
     FIG. 6 a  is a front schematic view of the brace corresponding to the position shown in FIG.  6 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, there is shown a brace  2  attached to a leg  11  of a wearer to lend support to the knee  13 . The brace is shown having an upper cuff  10  that fits about the thigh  14  of a user and a lower cuff  12  that fits about the upper calf  16 . A strap  17  extends between the upper and lower cuffs and wraps about the leg to retain the brace  2  on the leg. This attachment scheme is entirely conventional and other methods of securing the brace  2  to the leg are possible. 
     Upper cuff  10  is mounted to an upper arm  18  comprising essentially a rigid metal strip that is located by screws extending through the upper cuff  10  to engage in threaded openings  20  in arm  18  (FIG.  2 ). A lower arm  22  is attached to lower cuff  12  in a similar manner. 
     A pivotable joint  24  is formed at the ends of arms  18  and  22  to allow pivoting of the knee by pivoting movement of the arms. Joint  24  incorporates the novel locking mechanism of the present invention which acts to control pivoting of the joint to lock one of arms  18  or  22  in place relative to the joint while automatically unlocking the other arm to permit free pivoting movement as will be explained in more detail below. 
     As shown most clearly in FIG. 3, joint  24  is formed from bearings  26  and  28  which pivotally connect arms  18  and  22  to a link  30  which extend across the knee joint. Link  30  is formed from substantially circular bearing plates  32  and  33  that are joined together. The lower end of upper arm  18  is formed with a bearing plate  45  and the upper end of lower arm  22  is formed with a bearing plate  50 . 
     The various bearing plates  32 ,  33  of link  30  and the bearing plates  45  and  50  of the arms are all generally circular and have inner concave faces  36  and outer convex faces  37 . The bearing plates  45  and  50  of the arms are adapted to overlap and closely fit the bearing plates  32  and  33 , respectively, of link  30  to define dual bearings  26  and  28 . The inner concave surfaces  36  of plates  45  and  50  are readily slidable over the outer convex surfaces  37  of plates  32  and  33  to provide a smooth pivoting action. Preferably, as best shown in FIG. 4, inserts  42  made from a suitable low friction material such as plastic or the like and shaped appropriately are inserted between arm bearing plates  45 ,  50  and link bearing plates  32  and  33  to promote smooth pivoting movement of the joint. The inserts are preferably formed to be press fitted into place on the inner concave faces  36  of bearing plates  45  and  50 . 
     A cover  35  is also preferably provided to cover the arm bearing plates  45  and  50  as best shown in FIGS. 3 and 4. Cover  35  and link  30  act to sandwich plates  45  and  50  therebetween for pivotal movement. Cover  35  is not required but the cover does serve to protect and hide the movable bearing plates  45  and  50  of joint  24 . 
     Plates  32  and  45  of bearing  26  and plates  33  and  50  of bearing  28  are maintained in face-to-face sliding contact by means of pivot pins. As best shown in FIG. 2 and 4, the pivot pins preferably comprise bolts  62  and  63  that extend through clear holes  62   a  and  63   a , respectively, in cover  35  to engage threaded holes  62   b  and  63   b  in link  30 . In a similar manner, bolts  64  and  65  extend through clear holes  64   a  and  65   a  in cover  35  to engage threaded holes  64   b  and  65   b  in link  30 . 
     Arm bearing plates  45  and  50  are formed with arcuate slots  70 , 72 , 74  and  76  to permit passage of the bolts through the plates. The bolts and slots co-operate to define a plurality of pivoting axes for arms  18  and  22 , as indicated by arrows  78  and  80 , which are shiftable to accommodate the natural pivotal movement of the knee. 
     In the event that cover  35  is not present, the pivot pins can be posts that extend outwardly from the convex faces  37  of link  30  with enlarged heads that slidably engage the outer or convex faces  37  of bearing plates  45  and  50  to hold the bearing plates against separation from link  30 . 
     If low friction inserts  42  are present, they are also formed with appropriate slots  70   a , 72   a , 74   a  and  76   a  to accommodate the pivot pins. 
     The foregoing description of the brace structure is conventional and is generally disclosed in commonly owned patents such as U.S. Pat. No. 3,902,482 issued Sep. 2, 1975, U.S. Pat. No. 5,302,169 issued Apr. 12, 1994 and U.S. Pat. No. 5,400,806 issued Mar. 28, 1995. 
     According to the invention, joint  24  of brace  2  includes a locking mechanism to control the pivoting of the joint to lock one of the upper or lower arms  18 ,  22  relative to the joint while automatically unlocking the other arm to permit pivoting movement of the other arm about the joint. The locking mechanism acts to lock lower arm  22  in a default position relative to joint  24  until upper arm  18  is pivoted to a pre-determined position relative to the joint at which point the locking mechanism automatically locks upper arm  18  relative to the joint while lower arm  22  is unlocked to pivot. Lower arm  22  is free to pivot until the lower arm is pivoted back to its default position whereupon upper arm  18  is automatically unlocked and lower arm  22  is locked. 
     The default locked position of the lower arm  22  is illustrated in FIGS. 5 and 5 a . When the knee is straightened, the leg is essentially straight and the lower arm  22  is aligned with the lower leg in an essentially vertical position. 
     The pre-determined position of upper arm  18  that unlocks lower arm  22  occurs when the knee is flexed such that the upper arm is at an angle of approximately 40 degrees to the still essentially vertical lower arm as best shown in FIG. 6 a.    
     Automatic locking and unlocking of the upper and lower arms at the above-described positions allows the knee brace of the present invention to better support and control the movement of the knee so that the brace permits only natural knee movements. By virtue of the automatic locking of the upper and lower arms depending on their pivotal position, the knee brace prevents the arms from being forced past the normal range of knee movements. 
     As best shown in FIG. 4, in a preferred embodiment, the locking mechanism of the present invention comprises a rocker arm  85  positioned for pivotal movement about a pivot point adjacent the bearing plates  45 , 50  of the arms  18 , 22 . In the illustrated arrangement, the pivot point  86  for the rocker arm is formed on link  30  and preferably comprises a block of resilient material  87  fastened to link  30  to absorb vibration and noise. Slots  88  are cut through bearing plates  32  and  33  of link  30  to accommodate pivotal movement of rocker arm  85  on pivot point  86  through the generally spherical bearing plates. In addition, as best shown in FIGS. 5 and 6, cover  35  is preferably provided with a similar block of resilient material  105  which extends inwardly to engage rocker arm  85 . The rocker arm is thereby sandwiched between resilient blocks  87  and  105  to absorb vibration and noise to facilitate smooth pivoting of the rocker arm. 
     Rocker arm  85  has upper and lower protrusions  89  and  90 , respectively, at opposite ends of arm  85  on opposite sides of pivot point  86 . In the illustrated embodiment, protrusions  89  and  90  are shaped and dimensioned to be generally rectangular to be received in generally rectangular cavities formed on the concave inner face  36  of each of the arm bearing plates  45  and  50 . In particular, bearing plate  45  is formed with a cavity  91  to receive protrusion  89  and bearing plate  50  is formed with a cavity  92  to receive protrusion  90 . As best shown in FIG. 4, if low friction inserts  42  are used, the inserts are also formed with cavities  91   a  and  92   a  that are aligned with and fit into the corresponding cavities  91  and  92  formed in the arm bearing plates  45  and  50 . 
     As best shown in FIGS. 5,  5   a ,  6  and  6   a , the concave inner faces  36  of bearing plates  45  and  50  act as cam surfaces that engage protrusions  89  and  90  to bias rocker arm  85  such that one of the protrusions is always inserted into a cavity of one of the bearing plates to lock the arm associated with the bearing plate. For example, FIGS. 5 and 5 a  are section and front views, respectively, of the joint in a position in which upper arm  18  is free to pivot and lower arm  22  is locked in place in a substantially vertical orientation. Lower arm  22  is locked in position by virtue of lower rectangular protrusion  90  being inserted into rectangular cavity  92  on bearing plate  50 . Upper protrusion  89  is free to slide over the concave inner face  36  of bearing plate  45  which permits movement of arm  18 . Inner face  36  acts to bias rocker arm  85  in the direction indicated by arrows  100  to ensure that lower protrusion  90  remains in cavity  92  to lock the lower arm. 
     Cavities  91  and  92  are positioned and oriented on their respective bearing plates to define the locked position of the upper and lower arms. Note particularly in FIGS. 6 and 6 a  that as upper arm  18  is rotated associated bearing plate  45  rotates such that when arm  18  is rotated to a pre-determined angle of approximately 40 degrees to vertical, cavity  91  is aligned with and adjacent upper protrusion  89  of rocker arm  85 . At this position, either of arms  18  or  22  is free to pivot. Whichever arm moves will result in the protrusion adjacent the bearing plate for that arm moving out of the bearing plate cavity to engage the inner concave surface  36  of the bearing plate causing rocker arm  85  to pivot and the opposite protrusion to be inserted into the other cavity to lock the other arm. For example, if lower arm  22  is rotated in the direction indicated by arrow  102 , protrusion  90  will move out of cavity  92  to slide freely on inner concave face  36  of bearing plate  50 . At the same time, protrusion  90  moving on face  36  will cause rocker arm  85  to pivot about point  86  so that protrusion  89  will be inserted into cavity  91  to lock bearing plate  45  and upper arm  90  in the position indicated in FIG. 6 a.    
     To assist in the smooth movement of the rocker arm protrusions out of the cavities, both the protrusions and cavities are preferably formed with sloped surfaces. As best shown in FIGS. 5 and 6, upper protrusion  89  has a rounded contoured upper front edge  104  adapted to slide over a correspondingly contoured lip  105  at an upper edge of cavity  91 . In a similar manner, lower protrusion  90  has a rounded upper front edge  106  adapted to slide over rounded lip  107  of cavity  92 . Except for these cooperating rounded or sloped surfaces, protrusions  89  and  90  and cavities  91  and  92  have generally vertical sides to ensure that a protrusion is held locked within a cavity until such time as the bearing plates  45  and  50  are properly positioned to align both cavities with both protrusions, and one of the arms  18  or  22  is rotated in a direction that causes the rounded surfaces of a cavity and protrusion to engage and slide over each other. 
     From the above description, it will be apparent that the action of rocker arm  85  causes automatic locking of one arm against movement with respect to joint  24  while simultaneously unlocking the other arm for free pivoting. In this fashion, the knee brace of the present invention offers improved support for the knee as the locking of the upper and lower arms of the brace is designed to correspond to the normal range of movement of the knee joint so as to prevent abnormal anterior/posterior movement. 
     Although the present invention has been described in some detail by way of example for purposes of clarity and understanding, it will be apparent that certain changes and modifications may be practised within the scope of the appended claims.