Note: Descriptions are shown in the official language in which they were submitted.
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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:
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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
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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.
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[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:
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[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.
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[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
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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
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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.
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[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.
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[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
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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
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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
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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
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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.
