Detent mechanism for a hinged orthopedic brace

A hinge assembly is provided for an orthopedic brace having a rotatable hinge and a detent mechanism to automatically, yet releasably, lock the hinge in a fixed position of rotation. The hinge includes two rotatably attached members and the detent mechanism includes an indentation formed in the attached end of one member and a block pivotally mounted on the other member. The block has a locking projection that is biased toward the indentation and cooperates therewith to provide three positions of operation, a locked position, a release position, and an activated position. In the locked position, the locking projection fittingly engages the indentation, thereby substantially preventing rotation of the hinge. The release position displaces the locking projection a radial distance away from the indentation, thereby permitting the hinge to rotate freely. In the activated position, the block disengages the indentation and maintains an angular distance therefrom so that the detent mechanism does not obstruct rotation of the hinge, but enables automatic repositioning of the hinge assembly to the locked position whenever the locking projection and indentation angularly realign.

TECHNICAL FIELD 
The present invention relates generally to orthopedic braces, particularly 
to an orthopedic brace having a rotatable hinge, and more particularly to 
a detent mechanism for releasably locking a hinged orthopedic brace in a 
fixed position. 
BACKGROUND OF THE INVENTION 
Hinged orthopedic braces having an adjustable range of hinge rotation, as 
disclosed by U.S. Pat. Nos. 4,481,941 and 4,531,515, both to Rolfes, are 
known in the art. The braces disclosed therein have selectively 
positionable pins placed in predetermined holes about the hinge to act as 
stops limiting the range of hinge rotation and corresponding joint motion 
in accordance with the needs of the user. For example, it is oftentimes 
desirable to strictly limit the range of joint motion available to a 
patient immediately following surgery by limiting the range of hinge 
rotation that a brace positioned about the joint permits. The braces 
disclosed by the above-referenced patents are generally effective for this 
purpose. 
Although a limited degree of hinge rotation and corresponding joint motion 
can be desirable during rehabilitation of the joint, there are situations 
where it is advantageous to lock the hinge in a fixed position of 
rotation. For example, hinge rotation can be desirable when the patient is 
undergoing a controlled exercise regimen or when the patient is relaxing. 
Yet, the hinge is preferably maintained in a locked position when the 
patient initially resumes unsupervised activities, such as walking, to 
avoid reinjury to the joint before it is fully rehabilitated. 
As such, it is an object of the present invention to provide a hinge 
assembly for an orthopedic brace that enables a range of joint motion in 
one mode of operation and locks the joint into a fixed position in another 
mode of operation. It is another object of the present invention to 
provide such a hinge assembly that is operationally simple, requiring a 
minimum of user dexterity, skill and know-how. It is yet another object of 
the present invention to provide such a hinge assembly that readily 
transitions between the dynamic and static modes of operation with a 
minimal degree of user intervention. It is a further object of the present 
invention to provide such a hinge assembly that resists undesirable 
accidental repositioning of the assembly between the modes of operation. 
SUMMARY OF THE INVENTION 
The present invention is a hinge assembly for an orthopedic brace 
positionable about a joint to stabilize and support the joint. The hinge 
assembly has a rotatable hinge and a detent mechanism to releasably 
prevent rotation of the hinge in at least one direction. The detent 
mechanism is preferably configured to prevent rotation of the hinge and 
corresponding joint in the flexion direction when the hinge and joint are 
in a full extension position. 
The rotatable hinge includes a first elongated member having an end 
engaging an end of a second elongated member at a point of rotation. The 
detent mechanism comprises an indentation having a locking face which is 
formed at the end of the first member on the peripheral edge thereof. The 
detent mechanism further comprises a block pivotally mounted on the second 
member at a pivot point proximal to the end of second member. The block 
has a locking projection that protrudes therefrom and is biased toward the 
end of the first member by a block biasing spring. 
The hinge assembly is adjustably positionable to one of three positions, 
i.e., a locked position, a release position, or an activated position. The 
positions of the hinge assembly correspond to radial positions of the 
locking projection as the block is pivoted about its pivot point, and 
additionally correspond to angular positions of the hinge as the hinge is 
rotated about its point of rotation. 
In the locked position, the hinge is rotated until the locking projection 
is in angular alignment with the indentation, enabling the locking 
projection to radially pivot into the indentation under the force of the 
block biasing spring. The locking projection is configured to fittingly 
engage the indentation in abutment with the locking face, thereby 
substantially preventing rotation of the second member in the direction of 
the locking face. 
The indentation is preferably positioned on the first member such that 
angular alignment with the locking projection occurs when the hinge is 
rotated to full joint extension. Correspondingly, the locking face is 
preferably aligned to face away from the direction of flexion rotation of 
the first member. Thus, flexion rotation of the hinge from full joint 
extension is substantially impeded when the locking projection abuts the 
locking face. 
A release force counteracting the force of the block biasing spring is 
required to disengage the locking projection and indentation when the 
assembly is in the release position. The release force displaces the 
locking projection a radial distance away from the position it occupies 
when the assembly is in the locked position. The locking projection, and 
preferably the remainder of the block as well, is maintained radially 
clear of the second member in the release position, thereby permitting the 
hinge to rotate free of the detent mechanism. 
Unlike the locked position and the activated position described hereafter, 
the release position is solely dependent on the relative radial positions 
of the indentation and the locking projection. The release position is 
maintainable independent of the relative angular positions of the 
indentation and locking projection, whereas the indentation and locking 
projection must be angularly aligned to achieve the locked position and 
must be angularly unaligned to achieve the activated position. 
In the activated position, the hinge is rotated such that the block, 
including the locking projection, engages a relatively smooth segment of 
the peripheral edge an angular distance away from the indentation, while 
disengaged from the indentation. Although the block biasing spring biases 
the block radially against the edge in the activated position, the smooth 
surface of the segment enables slidable engagement of the block 
thereagainst. Accordingly, when the assembly is in the activated position, 
the detent mechanism does not obstruct rotation of the hinge. 
The present invention desirably enables automatic repositioning of the 
hinge assembly from the activated position to the locked position without 
operator intervention. The force of the block biasing spring automatically 
displaces the locking projection into the cooperatively configured 
indentation whenever the locking projection and indentation angularly 
align while the assembly is in the activated position. Conversely, the 
spring force and detent mechanism configuration desirably restrict 
unintentional repositioning of the assembly from the locked position to 
the release or activated position unless an external release force is 
intentionally applied to the block. 
A displacement arm radially extending from the block clear of the hinge is 
provided to facilitate application of an external release force to the 
block. The external release force is typically applied manually to the arm 
by the user, enabling radial displacement of the locking projection from 
the indentation, and correspondingly enabling repositioning of the 
assembly from the locked position to the release position or activated 
position. 
A displacement arm housing is also provided to facilitate retention of the 
assembly in the locked or release position. The housing pivotally engages 
the hinge, preferably on the second member, permitting removable 
positioning of the housing over the arm. Accordingly, manual access to the 
arm is enabled when the housing is pivoted to an open position and access 
to the arm is restricted when the housing is pivoted to a closed position. 
A housing biasing spring engages the hinge and housing to bias the housing 
in the closed position. 
A catch is situated in the housing to engage the displacement arm when the 
assembly is in the release position. The catch maintains the block and 
associated arm fixed in the release position, thereby preventing pivoting 
of the block into the locked or activated position. To reposition the 
assembly from the release position, the housing and correspondingly the 
catch are pivoted away from the hinge and displacement arm by a housing 
displacement force counter to the force of the housing biasing spring. The 
housing displacement force is preferably applied manually. 
If the locking projection is not angularly aligned with the indentation 
when the housing is pivoted away from the displacement arm, the assembly 
will automatically reposition into the activated position under the force 
of the block biasing spring. The assembly, however, will automatically 
reposition to the locked position, if the locking projection and 
indentation angularly align. 
The housing remains positioned over the displacement arm when the assembly 
is in the activated and release positions to prevent inadvertent 
impairment of block pivoting in the activated position or inadvertent 
release of the block in the locked position. When it is desired to return 
the assembly to the release position from the locked position, the housing 
is pivotally removed from over the displacement arm and the block is 
pivoted into the release position. The housing is then replaced over the 
displacement arm with the catch in engagement therewith. 
The detent mechanism of the present hinge assembly has utility in 
combination with rotatable hinges generally, as described above. The 
present detent mechanism has particular utility in combination with a 
specific rotatable hinge having at least one removable pin to 
supplementally limit the range of hinge and corresponding joint rotation. 
The limiting pin effectively defines a limited range of hinge rotation 
when the detent mechanism is in the release position. The detent 
mechanism, however, overrides the pin to substantially prevent any hinge 
rotation when the detent mechanism is in the locked position. 
The hinge of the present embodiment has one member with an end configured 
in the shape of a flat plate extending longitudinally therefrom. The plate 
has a plurality of spaced-apart holes formed through it in an arranged 
pattern. The end of the other member is fitted adjacent to the plate and 
the ends of the two members are rotatably attached by a fastener passing 
through aligned apertures therein. 
The limiting pin is sized to be received by the holes through the plate, 
the holes being arranged about the fastener. The limiting pin extends 
through the hole and behind the plate to engage the other member and block 
further rotation of the hinge in a given direction when the detent 
mechanism is in the release position. The limiting pin can be selectively 
placed in a particular hole to establish the desired range of hinge and 
corresponding joint rotation. When the detent mechanism is repositioned to 
the locked position via the activated position, rotation of the hinge is 
prevented, thereby overriding the effect of the limiting pin. 
The present invention will be further understood, both as to its structure 
and operation, from the accompanying drawings, taken in conjunction with 
the accompanying description, in which similar reference characters refer 
to similar parts.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring initially to FIG. 1, an orthopedic brace generally designated 10 
is shown having a hinge assembly 12 of the present invention. The 
particular orthopedic brace 10 described by way of example is a 
post-surgical knee brace fitted to the left leg 14 of a user. It will be 
apparent to one skilled in the art, however, that the hinge assembly 12 of 
the present invention can be incorporated into many other types of 
conventional hinged orthopedic braces applied to the knee, as well as to 
other joints including the hip, elbow or shoulder, without substantial 
modification in accordance with the instant teaching. 
The hinge assembly 12 includes a rotatable hinge 16 positioned at the knee 
joint 18 and a detent mechanism 20 adjacent to the hinge 16. A lower pivot 
bar, termed a first member 22, and an upper pivot bar, termed a second 
member 24, are substantially rigid support elements for the leg 14. A 
plurality of straps is provided in engagement with the first and second 
members 22, 24 to secure the brace to the leg, although only one lower and 
upper strap 25a, 25b is shown herein with the remainder omitted for 
clarity. The first and second members 22, 24 are integral components of 
the hinge 16 insofar as the hinge 16 is created by passing a rivet 26 
through the end 28 of the first member 22 and the end 30 of the second 
member 24, rotatably joining the ends 28, 30. 
The detent mechanism 20 includes a displacement arm 32 and a housing 34 
removably covering the arm 32. The housing 34 is pivotally attached to the 
second member 24 by means of a rivet 36 and is biased over the arm 32 by a 
housing biasing spring 38. Other components of the hinge 16 and detent 
mechanism 20 shown in FIG. 1 are displayed in greater detail in FIG. 2 
(with the straps omitted for clarity), and accordingly are described 
hereafter with reference thereto. 
The specific embodiment of the hinge 16 shown in FIG. 2 has similarities in 
construction to the hinge disclosed in copending U.S. patent application 
No. 07/907,480, which is incorporated herein by reference. Accordingly, 
the end 30 is configured in the form of two substantially parallel plates 
40 and 42. A gap 44 is created between the upper first plate 40 and the 
lower second plate 42. The end 28 fits in the gap 44 where it is rotatably 
secured to the parallel plates 40, 42 by the rivet 26 passing through the 
apertures 46a, 46b, 46c. The plates 40, 42 integrally form the end 30 of 
the second member 24 as a consequence of fixable attachment thereto by 
means of rivets 48 through apertures 50. 
A hinge rotation limiting pin 52 is shown extendable through the first and 
second plates 40, 42. The limiting pin 52 has an elongated cylindrical 
body 54 with a widened end 56. A plurality of spaced-apart holes 58 are 
formed through the first plate 40 in a circumferential pattern. The second 
plate 42 likewise has a plurality of spaced-apart holes 60 formed 
therethrough in the same pattern as the first plate 40 such that the holes 
58 are alignable with the holes 60. 
The body 54 of the limiting pin 52 is smaller in diameter than the holes 
58, 60, thereby enabling the holes 58, 60 to receive the limiting pin 52. 
The widened end 56, however, has a width greater than the diameter of the 
holes 58, 60 to prevent the limiting pin 52 from passing therethrough. In 
FIG. 2, the limiting pin 52 is shown to limit flexion rotation of the 
hinge 16 by abutting a flexion limiting face 62 formed on the end 28, but 
it is apparent that additional or substitute holes could be provided 
across the plates 40, 42 to similarly limit extension rotation of the 
hinge 16 by providing a limiting pin to abut an extension limiting face 64 
also formed on the end 28. 
In any case, interaction of the limiting pin 52 with the end 28 is 
incidental to the present invention insofar as operation of the limiting 
pin 52 is superseded by operation of the detent mechanism 20 when the 
mechanism 20 is in the locked position as will be shown hereafter. 
Referring further to FIG. 2, the detent mechanism 20 is shown to include a 
block 66 pivotally attached to the first and second plates 40, 42 by means 
of a rivet 68 through apertures 70a, 70b, 70c. The block 66 is preferably 
a unitary piece of metal machined to the configuration shown. 
Integral with the block 66 and extending therefrom are a locking projection 
72 and the displacement arm 32. The locking projection 72 is located on 
the block 66 proximal to the end 28, while the displacement arm 32 is 
located distal to the end 28 and extends from the block 66 to a position 
substantially clear of the second member 24. The locking projection 72 is 
configured to fit within a substantially v-shaped indentation 74 formed in 
the peripheral edge 76 of the end 28. A block biasing spring 78 is 
provided to bias the block 66 and associated locking projection 72 in the 
direction of the end 28. The spring 78 is a conventional torsion spring 
wedged between the block 66 and the second member 24. 
The housing 34 is shown in FIG. 2 to be pivotally attached to the second 
member 24 by the rivet 36 passing through apertures 80a, 80b. The housing 
34 preferably has a molded plastic construction enabling integration of 
the housing components into a unitary structure. In particular, the 
housing biasing spring 38 and a pair of catches (not shown in FIG. 2) 
internal to the housing 34 are preferably integrally formed with the 
housing 34. 
METHOD OF OPERATION 
Additional structural features of the present hinge assembly 12 are 
disclosed hereafter in conjunction with the operation of the assembly 12. 
The operating positions of the hinge assembly 12 are shown in FIGS. 3A, 
3B, and 3C to be a locked position, a release position, and an activated 
position, respectively. The operating positions of the hinge assembly 12 
correspond to radial positions of the block 66 and locking projection 72 
as the block 66 is pivoted about the rivet 68, and further correspond to 
angular positions of the hinge 16 as the hinge 16 is rotated about the 
rivet 26. 
Referring to FIG. 3A, the hinge assembly 12 is in the locked position, 
wherein the detent mechanism 20 prevents rotation of the hinge 16 in the 
flexion direction of the first member denoted by an arrow 82 when the 
hinge 16 is in a full extension position. Full extension is generally 
achieved when the flexion angle .theta. (see FIG. 3B) defined by the 
relative positions of the members 22, 24 is about 0.degree.. Flexion 
rotation of the hinge 16 is restricted by angular alignment of the locking 
projection 72 and indentation 74 and corresponding abutment of the locking 
projection 72 against a locking face 84 of the substantially v-shaped, 
albeit asymmetrical, indentation 74. 
The biasing force of the block biasing spring 78 has a radial component 
directed toward the indentation 74 to maintain the locking projection 72 
in close fit with the locking face 84 and prevent slippage therefrom. The 
locking position of the assembly 12 is further secured by engagement of 
the displacement arm 32 with a locking catch 88 in the housing 34. The 
biasing force of the housing biasing spring 38 also has a radial component 
that is directed toward the end 28 to maintain the housing 34 in a closed 
position and the displacement arm 32 in engagement with the locking catch 
88. 
The detent mechanism 20 shown herein is configured to prevent hinge 
rotation in only one direction, i.e., in the direction of flexion 82, by 
providing only one locking face 84 that is positioned to face away from 
the direction in which rotation of the first member 22 is restricted. 
Prevention of hinge rotation in the flexion direction 82 is enabled by the 
relative steepness of the locking face 84, acting as a catch for the 
locking projection 72. In contrast, the opposite face 90 of the 
indentation 74 is relatively shallow enabling substantially unhindered 
movement of the locking projection 72 therepast in the extension direction 
denoted by an arrow 92. 
It is further apparent to the skilled artisan that prevention of hinge 
rotation in the extension direction 92 can be provided by reconfiguring 
the indentation 74 with the locking face on the opposite side thereof. 
Similarly, restriction of hinge rotation in both directions can be 
provided by reconfiguring the indentation 74 to a substantially 
symmetrical v-shape with locking faces on both sides thereof, and 
correspondingly reconfiguring the locking projection 72. 
The cooperative embodiment of the locking projection 72 and indentation 74 
shown in FIG. 3A is nevertheless preferred insofar as the embodiment shown 
therein completely satisfies the desired objective of removably locking 
the hinge 16 in a position preventing joint flexion. In any case, the 
extension face 64 on the end 28 would stop against the block 66 before the 
extension angle .phi. (see FIG. 3B) substantially exceeds 180.degree.. 
It is noted that the limiting pin 52 is functionally inoperative when the 
hinge assembly 12 is in the locked position because hinge rotation is 
locked into a single angular position before the flexion face 62 abuts the 
pin 52. The limiting pin 52 only becomes operable when the hinge assembly 
12 is in the release or activated positions described hereafter with 
reference to FIGS. 3B and 3C, respectively. 
Referring to FIG. 3B, the hinge assembly 12 is in the release position, 
wherein the detent mechanism 20 does not substantially inhibit rotation of 
the hinge 16 in either the flexion or extension direction 82, 92. The 
release position is achieved by manually applying a force counteracting 
the force of the housing biasing spring 38 to pivot the housing 34 is 
denoted by an arrow 94. The manual force disengages the displacement arm 
32 from the locking catch 88 and exposes the displacement arm 32 to the 
user. 
Once exposed, a manual force having a radial component away from the end 28 
is applied to the displacement arm 32 to counteract the force of the block 
biasing spring 78, thereby pivoting the block 66 about the rivet 68. The 
arm 32 is correspondingly displaced in substantially the same direction as 
the arrow 94 and, in doing so, the locking projection 72 is radially 
displaced clear of the indentation 74. The housing 34 is released 
thereafter, enabling the release catch 96 to engage the displacement arm 
32 and passively maintain the assembly 12 in the release position. As a 
result, the hinge 16 is rotatable to a plurality of angular positions in 
either the flexion or extension direction substantially free of the detent 
mechanism 20. 
The limiting pin 52 is provided in the present embodiment to place an 
adjustable limit on flexion rotation of the hinge 16 when the detent 
mechanism 20 is in the release position. Thus, the present embodiment of 
the hinge assembly 12, providing the limiting pin 52 in conjunction with 
the detent mechanism 20, is desirable where it is advantageous to lock a 
joint into one fixed angular position in certain situations, while 
permitting rotation of the joint within a limited range of angular 
positions in other situations. It is, nevertheless, understood that the 
hinge assembly 12 disclosed herein remains operable in the absence of 
supplemental means for limiting the rotation range of the joint, such as 
the limiting pin 52 disclosed herein, when the assembly 12 is in the 
release position. In the absence of supplemental rotation limiting means, 
the hinge 16 simply rotates freely without restriction until the assembly 
12 is returned to the locked position. 
FIG. 3C shows the hinge assembly 12 in an activated position of operation 
achieved by manually reapplying a force to the housing 34 counteracting 
the housing biasing spring 38 to pivot the housing 34 away from the 
displacement arm 32 and disengage the displacement arm 32 from the release 
catch 96. The force of the block biasing spring 78 displaces the locking 
projection 72 in a radial direction against the end 28. The counter force 
on the housing 34 is withdrawn thereafter, and the housing biasing spring 
38 pivotally returns the housing 34 to a partially closed position, 
wherein the housing biasing spring 38 likewise exerts a biasing force on 
the displacement arm 32 in the direction of the end 28. 
The indentation 74 is preferably angularly displaced away from the locking 
projection 72 when the projection 72 radially approaches the end 28 such 
that the projection 72 slidably engages the end 28 along a segment 98 of 
the peripheral edge 76 away from the indentation 74. The segment 98 is 
relatively smooth and continuous enabling the hinge 16 to rotate freely 
within the angular range of slidable engagement between the block 66 and 
the segment 98. This range is limited in the flexion direction 82 of the 
first member 22 by the limiting pin 52 and is limited in the extension 
direction 92 of the first member 22 by the block 66. The hinge 16 is shown 
in FIG. 3C rotated to the flexion limit occurring when the limiting pin 52 
abuts the flexion face 62. 
When the hinge assembly is in the activated position, the block 66 is free 
to pivot about the rivet 68 under the force of the block biasing spring 78 
because the displacement arm 32 is substantially clear of both catches 88, 
96 and the locking projection 72 is clear of the indentation 74, being a 
greater radial distance away from the first member 22 relative to the 
locked position. Thus, the block follows the contour of the segment 98 as 
the hinge 16 rotates. However, when the hinge 16 is rotated to a point 
where the locking projection 72 and indentation 74 are angularly aligned, 
the assembly 12 automatically repositions from the activated position to 
the locked position of FIG. 3A. 
The hinge assembly 12 of the present invention has particular utility where 
it is desirable to permit some rotation of the hinge 16 in a relaxed 
flexion position while the user is substantially at rest, but to lock the 
hinge 16 into a fixed extension position when the user resumes activity, 
such as when the user transitions from a passive sitting position to an 
active walking position. Since it is difficult for the user to manually 
access the assembly 12 while it is adjacent to the knee joint at full 
extension, the present invention enables the user to set the assembly 12 
to the activated position while in flexion. When the user subsequently 
stands up to full extension, the assembly 12 automatically locks without 
any further user intervention. 
While the forgoing preferred embodiments of the invention have been 
described and shown, it is understood that alternatives and modifications, 
such as those suggested and others, may be made thereto and fall within 
the scope of the invention. Thus, although the above-recited hinge 
assembly 12 has been shown to include a specific preferred embodiment of 
the rotatable hinge 16, it is apparent that the present detent mechanism 
20 can be readily adapted to cooperate with other known rotatable hinge 
constructions and such hinge assemblies are within the scope of the 
present invention. In particular, it is within the purview of the skilled 
artisan to practice the present invention relying on the detent mechanism 
to restrict hinge rotation absent the limiting pin, and with or without 
the cooperation of alternate supplemental means for restricting hinge 
rotation.