CA2563915A1 - Knee brace and hinge mechanism for knee brace - Google Patents

Abstract

knee brace has a hinge mechanism between upper and lower portions, the hinge mechanism having connected upper and lower members attachable to the upper and lower portions of the brace. The hinge mechanism also has a pad for applying pressure to a side of a wearer's knee, for among other reasons to guide a user's knee in a natural motion during knee flexion and extension. A four-bar hinge provides posterior translation immediately prior to rotation, avoiding a "pistoning" effect between upper and lower portions of the knee brace. A
compliant stop is provided in the hinge to prevent over-extension of the knee and to prevent jarring of the knee when the knee is extended. The hinge has a sliding plate onto which the pad is mounted, which moves posterially with the skin of the user when the knee is flexed, thereby avoiding excessive skin abrasion and irritation. To further avoid skin and underlying tissue irritation, the pad may also be gel or foam-filled, and may have a surface made of a slippery material.

Description

KNEE BRACE AND HINGE MECHANISM FOR KNEE BRACE
Cross Reference to Related Application [0001] This application claims the benefit of the filing date of US
patent application No. 60/561,896 filed on 14 April, 2004, which is hereby incorporated herein by reference.
Technical Field (0002] This invention relates to knee braces.
B ack rg ound [0003] Knee braces are worn by athletes to protect their knees and by individuals whose knees have been weakened or rendered painful or unstable as a result of accident, surgery, arthritis, or the like. Knee braces typically include a part that attaches to a person's upper leg, a part that attaches to the person's shin, and hinges connecting .the upper and lower parts. Reid, Spots Injuy Assessme~Zt and Rehabilitation, (1992) Churchill Livingstone Inc., New York, New York USA ISBN 0-443-08662-1 describes some of the challenges encountered in treating injuries and other knee conditions.

[0004] The design of the hinges in a knee brace is important in the proper operation of the knee brace as the hinges determine how the knee brace will guide the motions of a wearer's knee. When a person flexes their knee starting from a fully extended position, the tibia undergoes a posterior translation and then begins to rotate. It is desirable to provide a hinge that can guide a knee that is unstable as a result o~ ligament laxity (e.g. not properly supported), and/or apply corrective forces to address osteoanthritis, and/or guide a knee that is under unusual pressure to flex in a natural way.

[0005] Various knee braces hinges are described in the patent literature. For example, knee brace hinges are described in:

_2_ May, US 3,901,223;

Lamb et al., US 4,523,585 and RE
33,621;

Lerman, US 4,628,916;

Detty, US 4,715,363;

Townsend, US 4,723,539;

Townsex~d, US 4,773,404;

Audette, US 4,821,707;

Castillo et al., US 4,886,054;

Townsend, US 4,890,607;

Harris et al., US 4,938,206;

Moore et al., US 4,961,416;

Defonce, US 5,009,223;

Weidenburner, US 5,022,391;

Rasmusson, US 5,060,640;

Rogers et al., US 5,107, 824;

Silver et al., US 5,230,696;

Townsend, US 5,259, 832;

Meyers et al., US 5,286,250;

Townsend, US 5,330,418;

Tamagni, US, 5,372,572;

Luttrell et al., US 5,547,464;

Kubein-Messenberg et al., US 5,800,370;

Castillo, US 6,464,657; and, Pellis, US 6,358,190.

[0006] Hinges are a wealc point in many current knee brace designs.
Hinges in some knee braces suffer from one or more of the disadvantages that they are: insufficiently robust, are not rigid enough to provide adequate knee support, do not allow the knee to move in a natural manner, do not properly mimic the articulation of the knee joint correctly, do not permit adequate correction forces to be applied to the knee, or have other disadvantages.

[0007] Some knee braces (sometimes referred to as "unloader"
braces) are designed to provide significant lateral force on one side of the knee or the other. By applying a lateral force to one side of the knee, one can relieve pressure on the condyle on the opposite side of the knee. This can be important for example, in relieving pain due to osteoarthritis in the knee joint. Arthritis often affects one compartment of the knee joint more than the other. The affected compartment can tend to collapse. By applying a force on the side of the knee opposite to the affected compartment one can relieve pressure on the affected compartment. In some cases it is desirable to apply forces to both sides of a knee to assist in stabilizing a knee with ligament injuries and/or instability.

(0008] Many knee braces have insufficient structural integrity to act as platforms for providing a desired degree of lateral pressure on a wearer's knee. This is true particularly when the wearer is large in stature or very athletic. Another problem with knee braces which have a part that exerts lateral force on the knee is that the part can be uncomfortable and may cause abrasion of the skin and irritation to underlying tissues of the knee.

[0009] Further, many knee braces are structurally unable to dampen the shock of the hyperextension of the knee. Many such braces have, only hard "stops" which jar the knee in extension, causing the tissues and/or bones therein to impact against one another, while it would be preferable to decelerate extension with a more compliant stop mechanism to avoid such hard shocks to the knee. This is especially an issue with ACL/posterior capsule damage.

[0010] There is a need for knee braces, and for component parts for knee braces, which can alleviate at least some of the disadvantages of prior art knee brace technology.
Surnmar~of the Invention [0011] One aspect of the invention provides a hinge mechanism for a knee brace. The hinge mechanism connects upper and lower members and includes a pad for applying pressure to a side of a wearer's knee. The pad is mounted to an arm that is pivotally connected to one of the upper and lower members and is slidably and pivotally coupled to another one of the upper and lower members. Preferably the arm is slidably and pivotally coupled to the upper member. The hinge mechanism may be applied in a knee brace by j oining the upper member to an upper portion of the knee brace and joining the lower member to a lower portion of the knee brace.
The upper portion of the knee brace can be attached to a wearer's leg above the knee while the lower portion of the knee brace is attached to the wearer's leg below the knee.

[0012] Another aspect of the invention provides a hinge mechanism for a knee brace. The hinge mechanism comprises a two-stage stop mechanism. The stop mechanism is configured to resist further extension of the hinge mechanism beginning 5 to 20 degrees before the hinge mechanism reaches a fully-extended position.

[0013] Further aspects of the invention and features of embodiments of the invention are described below.
Brief Description of the Drawings [0014] In drawings which illustrate an example embodiment of the 3 0 invention:

[0015] Figure 1 is an exploded view of a knee brace hinge according to one embodiment of the invention;

[0016] Figures 2A, 2B, 2C, 2D and 2E are respectively drawings illustrating the knee brace hinge of Figure 1 in various positions between a fully flexed position shown in Figure 2A and a fully extended position shown in Figure 2E as seen from an inside of the hinge (i.e. a side of the hinge facing toward a wearer's knee).

[0017] Figures 3A, 3B, 3C, 3D and 3E are respectively drawings illustrating the knee brace hinge of Figure 1 in various positions between a fully flexed position shown in Figure 3A and a fully extended position shown in Figure 3E as seen from the inside of the hinge with the slider plate removed.

[0018] Figure 4 is a view of the knee brace hinge of Figure 1 from a medial side with a knee-contacting pad removed to show a mechanism for permitting limited rotation of the cup.

[0019] Figure 5 is schematic view illustrating a geometric configuration of the linkage of the hinge of Figure 1.

[0020] Figure 6 is a isometric view of the hinge of Figure 1 and Figure ~A is a front view of the knee brace hinge of Figure 1.

(0021] Figures 7A through 7D are views of a hinge like that of Figure 1 equipped with different knee-extension stops which engage at different degrees of extension. Figure 7E is a view of a hinge without a knee-extension stop.

[0022] Figure 8 is a sketch showing a knee brace according to the invention, in a side view.

[0023] Figure 8A is a sketch of the brace shown in Figure 8, in a top perspective view.

[0024] Figure 9 is a schematic section through a knee joint at the level of the tibial plateau.

[0025] Figure 10 is a cross sectional view through a pad of the knee brace hinge of Figure 1.
Description [0026] Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention.
However, the invention may be practiced without these particulars. In other instances, well known elements have .not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

[0027] The knee brace hinge shown in the accompanying drawings has been developed by the inventors to address a number of issues. Not all embodiments of the invention necessarily address all of these issues. One issue is to provide a hinge mechanism that can guide a user's knee in a natural motion during knee flexion and extension. This issue is addressed in the illustrated embodiment by providing a four-bar hinge mechanism having an overall geometry as shown in Figure 5. The four-bar hinge provides posterior translation immediately prior to rotation, avoiding a more typical "pistoning" effect between upper and lower portions of a knee brace.

[0028] Another issue is to provide a knee brace that can apply pressure to one or both sides of a wearer's knee without causing excessive skin abrasion. This issue is addressed in the illustrated embodiment by providing a slider plate mechanism to carry a knee-contacting pad as shown, for example, in Figures 2A to ZE. Another issue is to provide a stop that can prevent over-extension of the knee without jarring when the stop is reached. This issue is addressed in the illustrated embodiment by providing a compliant stop mechanism as shown, for example, in Figures _' 3A to 3E . Another issue is to reduce discomfort caused by pressure of a knee-contacting pad on bony prominences of the knee. This issue is addressed in the illustrated embodiment by providing a pad comprising a gel or other material having similar properties.

[0029] Figures 1 through 6A show a hinge 10 for a knee brace according to one embodiment of the invention. As seen best in Figures l, 5 and 6, hinge 10 includes an upper arm 12 which is connected to a lower arm 14 by a four-bar linkage mechanism 16. As shown in Figure 8, upper arm 12 may be attached to upper portion 82 of a knee brace 80 and lower arm 14 may be attached to a lower portion 84 of knee brace 80. A hinge 10 for a right-hand side of a knee brace 80 can be a mirror image of a hinge 10 for a left-hand side of a knee brace 80. Upper portion 82 can be attached to a wearer's leg above the knee while lower portion 84 can be attached to the wearer's leg below the knee with suitable straps or the like (Figures 8 and 8A).

[0030] Four-bar linkage mechanism 16 permits lower arm 14 to pivot relative to upper arm 12 with a motion which generally mimics the typical action of a human knee. When a human knee is flexed, beginning from a position in which the lower leg is fully extended, in a first phase of flexion, the tibia shifts posteriorly relative to the femur. In a second phase of motion the tibia rotates about the axis of instantaneous centre of rotation of the 'knee relative to the femur. The position of the knee axis of rotation changes as the knee flexes.

[0031] Four-bar linkage 16 comprises first and second links 20 (Figure 5) and 22 which are each pivotally connected to upper arm 12 and lower arm 14. Links 20 and 22 may be mounted on opposite sides of upper arm 12 and lower arm 14 from one another. In the illustrated embodiment, link 20 is on an outside of upper and lower arms (i.e. the side of the upper _g_ and lower arms facing away from the wearer's knee) while link 22 is on an inside of the upper and lower arms (i.e. the side of the upper and lower arms facing toward the wearer's knee).

[0032] Figure 5 illustrates a possible geometry of links 20 and 22.
Link 20 pivots relative to upper arm 12 at pivot axis 23C and pivots relative to lower arm 14 about pivot axis 23D. Pivot axes 23C and 23D
can also be seen in Figure 1.

[0033] In the illustrated embodiment, link 20 is pivotally affixed to cylindrical posts 31 and 33 (Figure 1), which project respectively from upper and lower arms 12 and 14 through corresponding apertures in link 20, by screws 24 and washers 25. Any suitable alternative mechanisms for pivotally attaching link 20 to upper arms 12 and lower arms 14 could be used.

[0034] Similarly, linlc 22 is pivotally mounted to upper arm 12 for rotation about pivot axis 23A and lower arm 14 for rotation about pivot axis 23B by posts 37 and 39 (Figure 1). Link 22 is mounted to a cylindrical post 37 which projects from upper arm 12 through a corresponding aperture in link 22 by screw 27. Link 22 is mounted to a cylindrical post 39 which projects though a corresponding aperture in link 22 by screw 26. Those slcilled in the art will appreciate that alternative means for pivotally mounting link 22 to upper and lower arms 12 and 14 could be provided.

[0035] When hinge 10 is used to connect upper part 82 and lower part 84 of a knee brace 80 (see Figure ~), four-bar linkage 16 permits lower part 84 to translate posteriorly and then rotate in a way which is compatible with the desired motion of a flexing knee.

[0036] When it is desired to apply a force to the side of a wearer's knee on which hinge 10 is located, hinge 10 carries a slider plate (described below) which ca1-ries a cup 30 which supports a pad 32. Pad 32 is shown in cross-sectional detail in Figure 10. Pad 32 may be, for example, be filled with a gel 70 which can conform to the contours of the medial or lateral side of a wearer's knee. Pad 32 may be detachably affixed to cup 30 with a hook and loop fastener material 72 such as VelcroTM.
Cup 30 is preferably resiliently flexible. The position of cup 30 may be adjusted (as described more below) in order to apply a desired degree of force to an appropriate area on a desired side of the wearer's knee. A cup 30 and pad 32 may be provided on one or both sides of a knee brace 80.

[0037] When a human lc~zee flexes, the skin over the knee moves significantly from an anterior position to a posterior position relative to the underlying bones, tendons and ligaments. So that pad 32 will not abrade the wearer's skin, it is desirable to mount pad 32 in such a manner that it tends to move in a way which follows the motion of the skin on the wearer's knee as the wearer flexes his or her knee (ie. posterially). This reduces tissue shear, which can be uncomfortable and which will often result in skin and tissue breakdown. As shown in Figure 9, it is generally desirable for pads 32 to move generally posteriorly as indicated by arrows 133 as the knee is flexed, following the curvature of the knee generally, and in an anterior direction (shown by arrows 135) as the knee is extended.
The motion of pad 32 is also illustrated in Figures 2A (full flexion) and 2E
(full extension), which show the position of a reference point 90 relative to the intersection of the longitudinal axes of arms 12 and 14.

[0038] It is also desirable to .face pad 32 with a material that has a low coefficient of friction with skin. Pad 32 may be faced with a slippery LycraTM or TeflonTM material 74 for example.

- 1~ -[0039] Pad 32 is preferably filled with a material, such as a silicone gel or a suitable foam 70, which is resilient to shear forces but which has a memory (i.,e. after it has been deformed it tends to return to its original shape). Such a material is desirable because it can flow over and/or past bony prominences~in the area of the wearer's knee, tending to keep relatively even the pressure exerted on the knee by the entire pad surface.

[0040] In the illustrated embodiment, cup 30 is mounted to a slider plate 34. Slider plate 34 is pivotally mounted to lower and upper arms 12 and 14. Slider plate 34 is longer than links 20 and 22 of four-bar linkage 16. Preferably, either:
~ the upper mounting point of slider plate 34 is above upper pivot axes 23A and 23C of four-bar linkage 16;
~ the lower mounting point of slider plate 34 is below lower pivot axes 23B and 23D of four-bar linkage 16; or, ~ the upper mounting point of slider plate 34 is above upper pivot axes 23A and 23C of four-bar linkage 16 and the lower mounting point of slider plate 34 is below lower pivot axes 23B and 23D of four-bar linkage 16.

[0041] Preferably, as shown in Figure 2A, a lower end of slider plate 34 is pivotally mounted to lower arm 14 for rotation about pivot axis 23D.
The lower ends of slider plate 34 and link 22 pivot about the same axis. In the illustrated embodiment, as can best be seen in Figure 1, the same screw 26 which affixes the lower end of link 22 to lower arm 14 also holds the lower end of slider plate 34 by way of a stepped bushing 26A.

[0042] The upper end of slide plate 34 is mounted to upper 12 at a location 35 which is above both pivot axes 23A and 23C. In the illustrated embodiment, the upper end of slider plate 34 is free to both slide and pivot about a stepped bushing 35A held by a screw 35B. Slider plate 34 has a slot 36 which permits pivot axis 35 to move up and down relative to slider plate 34 as hinge 10 is flexed. With this arrangement, cup 30, mounted on slider plate 34, follows more naturally the motion of the tissues on the side of the wearer's knee as the wearer flexes his or her knee. Consequently, such a knee brace can be used to apply significant forces to the side of the wearer's knee while avoiding undesirable complications such as excessive skin abrasion (chafing) that could be caused by the application of repetitive shear forces to the skin of a wearer's knee.

[0043] Cup 30 is held in place by a retainer 42 and a screw, or other suitable fastener, 43. The position of cup 30 in an anterior-posterior direction is preferably adjustable to suit a wearer. In the illustrated embodiment, a number of alternative mounting points 45A, 45B and 45C
are provided on slider plate 34 for cup 30. Screw 43 may be screwed into any of mounting points 45A, 45B or 45C in order to position cup 30 in a desirable position.

[0044] Cup 30 may be mounted directly to slider plate 34 or spaced apart from slider plate 34 in a direction toward the wearer's knee by a spacer 40. The thickness of spacer 40 may be selected to provide a desired degree of pressure on the side of a wearer's knee. In the illustrated embodiment, one spacer 40 is shown. In some embodiments of the invention, multiple spacers may be staclced and the number and/or thicknesses of spacers 40 may be varied to allow cup 30 to be spaced apart from slider plate 34 by a desired distance.

[0045] It is desirable to provide some means for limiting the rotation of cup 30 to a small angle, such as about 10, 15 or 20 degrees. In the illustrated embodiment (see Figure 4) a pin 46 engages a cutout 48 in a cup 30. The angular extent of cutout 48 relative to the center of cup 30 determines how far cup 30 can rotate. Rotation of cup 30 is stopped by pin 46 abutting the edges of cutout 48. Pin 46 may be on a spacer 40, as shown, or may project from slider plate 34.
[0046] Where a spacer 40 is provided between cup 30 and slider S plate 34 it is desirable to provide a means for preventing spacer 40 from turning relative to slider plate 34. For example, spacer 40 may include a pin 47 (see Figure 1) which is inserted into one of apertures 49A, 49B or 49C to prevent spacer 40 from rotating relative to slider plate 34. In the alternative, a pin or other projection (not shown) may project from slider plate 34 into an indentation in spacer 40.

[0047] In some embodiments of the invention, spacer 40 includes an indentation corresponding to each of pins 46 and 47 so that several spacers 40 can be stacked together with the pin 47 of the one of spacers 40 closest to spacer plate 34 engaged in the one of apertures 49A, 49B or 49C which corresponds to the mounting point to which cup 30 is mounted. The pin 46 of the spacer 40 closest to slider plate 34 is engaged in the indentation of the adjacent spacer 40. The pin 46 of the spacer 40 closest to cup 30 is engaged in cutout 48 of cup 30.

[0048] Cup 30 is preferably made of a moldable material which can be shaped to conform appropriately to the shape of a wearer's knee. For example, cup 30 may be made of a heat moldable material. One material suitable for cup 30 is Kydex, a thermoplastic alloy available from I~leerdex Company of Bloomsburg, Pennsylvania, USA.

[0049] Hinge 10 includes a stop mechanism 60 (Figure 3). Stop mechanism 60 prevents over extension of a wearer's knee. In a preferred embodiment of the invention, stop mechanism 60 is a two-stage stop mechanism. The two-stage stop mechanism 60 begins to resist further extension of hinge 10 a few degrees (e.g. 5 to 20 degrees) before hinge 10 reaches its fully extended position. This tends to decelerate motion of a wearer's tibia. Then, when hinge 10 is reaching its fully-extended position, two-stage stop mechanism 60 provides a definite, but cushioned, stop to the motion of hinge 10.

[0050] Stop mechanism 60 includes a cam portion 62 on link 22.
Cam portion 62 engages stop 63. In the illustrated embodiment, cam portion 62 has an edge 64 (see Figure 3A). Stop 63 includes a spring 66 which is mounted to upper arm 12. In the illustrated embodiment, spring 66 comprises a leaf spring having one end retained in a slot within a body 67 of stop 63. A screw 69 may optionally be provided to secure spring 66 and/or adjust the preload of spring 66.

[0051] As hinge 10 is moved from its fully flexed position (shown in Figure 3A) towards its fully extended position (shown in Figure 3E), spring 66 initially rides against a portion of edge 64 which has a relatively constant curvature and at least generally follows an arc centered on pivot axis 23C (see Figures 2B, 2C and 2D).,It is optional for spring 66 to contact edge 64 during this part of the range of motion of hinge 10.

(0052] As hinge 10 nears its fully-extended position, spring 66 comes into contact with a straighter portion 64A of edge 64. In some embodiments this begins to occur at approximately 15 or 20 degrees before full extension. From this point, further rotation of hinge 10 tends to compress spring 66. Spring 66 begins to resist the further extension of hinge 10. Spring 66 may be fabricated from a shape-memory alloy having relatively large strain and fatigue limits. Spring 66 may comprise two or more leaves.

[0053] The angle at which stop mechanism 60 stops further extension of hinge 10 may be adjusted by selecting and installing an appropriate link 22 from an assortment of links 22 having cam portions 62 having differently shaped edges. Figures 7A-7E show a hinge with different links 22.

[0054] Stop 63 includes a bumper 68 which is on a side of spring 66 away from edge 64. Ultimately, spring 66 is brought into contact with bumper 68. The stop provided by bumper 68 is dampened but definite. In the illustrated embodiment, cam edge 64 presses spring 66 directly against bumper 68. Preferably bumper 68 is made of a soft resilient material such as silicone. The combination of spring 66 and bumper 68 provides a soft stop which avoids j arcing of a wearer's knee when hinge 10 reaches full extension while a wearer is wearing the knee brace.

[0055] The various parts of hinge mechanism 10 may be made from any suitable materials. In a prototype embodiment of the invention, links and 22 are made of DeliinTM and upper and lower arms 12 and 14 and slider plate 34 are made from stainless steel.

[0056] As will be apparent to those skilled in the art in the light of 20 the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the scope thereof.

Claims (45)

1. A hinge mechanism for a knee brace, the hinge mechanism connecting upper and lower members and including a pad for applying pressure to a side of a wearer's knee wherein the pad is mounted to an arm pivotally connected to one of the upper and lower members and slidably and pivotally coupled to another one of the upper and lower members.

2. A hinge mechanism according to claim 1 wherein the arm is slidably coupled to the upper one of the upper and lower members.

3. A hinge mechanism according to one of claims 1 and 2 wherein an upper end of the arm carries a slot and a pivot member attached to the upper member is slidably disposed within the slot.

4. A hinge mechanism according to one of claims 1 to 3 comprising a four-bar linkage coupling the upper and lower members, the four-bar linkage comprising first and second links each pivotally coupled to each of the upper and lower members.

5. A hinge mechanism according to claim 4 wherein one of the first and second links is on a first side of the upper and lower members and the other of the first and second links is on a second side of the upper and lower members opposed to the first side.

6. A hinge mechanism according to claim 4 or 5 wherein the arm is longer than either of the first and second links.

7. A hinge mechanism according to claim 6 wherein a lower end of the arm and one of the first and second links are both pivotally mounted to the lower member for pivoting about a common axis.

8. A hinge mechanism according to any one of claims 4 to 7 wherein the first and second links are pivotally connected to the upper member at locations that are more closely spaced than locations at which the first and second links are pivotally coupled to the lower member.

9. A hinge mechanism according to claim 4 wherein one of the first and second links lies between the arm and the upper and lower members.

10. A hinge mechanism according to any one of claims 1 to 9 comprising a stop mechanism disposed to limit extension of the hinge mechanism.

11. A hinge mechanism according to claim 10 wherein the stop mechanism is a two-stage stop mechanism.

12. A hinge mechanism according to claim 11 wherein the stop mechanism begins to resist further extension of the hinge mechanism 5 to 20 degrees before the hinge mechanism reaches a fully-extended position.

13. A hinge mechanism according to any one of claims 10 to 12 wherein the stop mechanism includes a leaf spring and a cam surface that deflects the leaf spring as the hinge moves toward a fully-extended position.

14. A hinge mechanism according to claim 13 wherein the stop mechanism comprises an elastomer stop and the leaf spring is located between the elastomer stop and the cam surface.

15. A hinge mechanism according to claim 13 or 14 wherein the leaf spring comprises a plurality of leaves.

16. A hinge mechanism according to any one of claims 13 to 15 wherein the cam surface is a surface on a link of the four bar linkage.

17. A hinge mechanism according to claim 16 comprising a plurality of interchangeable links for the four bar linkage, each of the interchangeable links having a cam surface having a profile different from profiles of other ones of the plurality of interchangeable links.

18. A hinge mechanism according to claim 16 or 17 wherein, when the hinge mechanism is in a flexed position, the leaf spring engages a portion of the cam surface having an essentially constant radius.

19. A hinge mechanism according to any one of claims 10 to 18 wherein the stop mechanism comprises an elastomer stop.

20. A hinge mechanism according to any one of claims ,10 to 19 wherein the stop mechanism is disposed between the arm and the upper and lower members.

21. A hinge mechanism according to any one of claims 1 to 10 comprising:
a means for resisting further extension of the hinge mechanism 5 to 20 degrees before the hinge mechanism reaches a fully-extended position; and, a means for providing a cushioned stop to the motion of the hinge mechanism when the hinge mechanism is reaching its fully-extended position.

22. A hinge mechanism according to any one of claims 1 to 21 wherein the arm comprises a plurality of mounting locations and the pad is mountable to any selected one of the mounting locations.

23. A hinge mechanism according to any one of claims 1 to 22 wherein the pad comprises an outer layer enclosing a body of a gel.

24. A hinge mechanism according to claim 23 wherein the gel comprises a resilient gel having a memory.

25. A hinge mechanism according to claim 23 wherein the gel comprises a silicone gel.

26. A hinge mechanism according to any one of claims 1 to 25 wherein the outer layer of the pad comprises a slippery material.

27. A hinge mechanism according to any one of claims 1 to 26 wherein the pad is supported on a cup of a resiliently flexible material.

28. A hinge mechanism according to claim 27 wherein the resiliently flexible material of the cup is thermoformable.

29. A hinge mechanism according to any one of claims 1 to 28 comprising a spacer between the pad and the arm.

30. A hinge mechanism according to claim 29 comprising a plurality of spacers between the pad and the arm.

31. A hinge mechanism according to claim 30 wherein the spacers are engaged with one another to prevent rotation of the spacers relative to one another.

32. A hinge mechanism according to any one of claims 1 to 31 wherein the pad is free to rotate through a limited angular range about an axis extending generally at right angles to the arm.

33. A hinge mechanism according to claim 32 wherein limited angular range has an extent in the range of 5 to 25 degrees.

34. A knee brace comprising an upper part for connecting to a wearer's leg above the knee of a wearer, a lower part for connecting to a wearer's leg below the knee and a hinge mechanism according to any one of claims 1 to 33 connected between the upper and lower parts.

35. A hinge mechanism for a knee brace comprising a two-stage stop mechanism, the stop mechanism configured to resist further extension of the hinge mechanism 5 to 20 degrees before the hinge mechanism reaches a fully-extended position.

36. A hinge mechanism according to claim 35 wherein the stop mechanism includes a leaf spring and a cam surface that deflects the leaf spring as the hinge moves toward a fully-extended position.

37. A hinge mechanism according to claim 36 wherein the stop mechanism comprises an elastomer stop and the leaf spring is located between the elastomer stop and the cam surface.

38. A hinge mechanism according to claim 36 or 37 wherein the leaf spring comprises a plurality of leaves.

39. A hinge mechanism according to any one of claims 35 to 38 comprising a four-bar linkage coupling the upper and lower members, the four-bar linkage comprising first and second links each pivotally coupled to each of the upper and lower members, wherein the cam surface is a surface on a link of the four bar linkage.

40. A hinge mechanism according to claim 39 comprising a plurality of interchangeable links for the four bar linkage, each of the interchangeable links having a cam surface having a profile different from profiles of other ones of the plurality of interchangeable links.

41. A hinge mechanism according to claim 39 or 40 wherein, when the hinge mechanism is in a flexed position, the leaf spring engages a portion of the cam surface having an essentially constant radius.

42. A hinge mechanism according to claim 35 comprising:
a means for resist further extension of the hinge mechanism 5 to 20 degrees before the hinge mechanism reaches a fully-extended position; and, a means for providing a cushioned stop to the motion of the hinge mechanism when the hinge mechanism is reaching its fully-extended position.

43. A knee brace comprising an upper part for connecting to a wearer's leg above the knee of a wearer, a lower part for connecting to a wearer's leg below the knee and a hinge mechanism according to any one of claims 35 to 42 connected between the upper and lower parts.

44. Apparatus comprising any new inventive feature, combination of features or sub-combination of features described herein.

45. Methods comprising any new inventive step, act, combination of steps and/or acts or sub-combination. of steps and/or acts described herein.