Patent Publication Number: US-9844448-B2

Title: Prosthetic knee

Description:
FIELD OF THE INVENTION 
     The invention relates to a prosthetic knee in a prosthetic leg assembly, and more particularly to a prosthetic knee including a four bar geometry adapted for athletic uses. 
     BACKGROUND 
     Artificial limbs, including leg prostheses, employ a wide range of technologies to provide solutions suitable to many differing needs. For a trans-femoral amputee, basic needs in a leg prosthesis include stability, while standing and during the stance phase of a walking gait, and mechanical compatibility with the walking (or running) gait and some manner of knee flexion during stance and swing phases of a gait. 
     Certain trade-offs exist between security and stability, and walking or running performance (dynamic behavior). A simple, non-articulable leg (having no movable knee), may provide maximum stability, but does not provide for an ideal gait. Also, sitting may be awkward if a person cannot bend their knee. 
     There are no prosthetic knees tailored for high activity users, particularly athletes. For example, above-the-knee amputee sprinters and runners typically must resort to prosthetic knees designed primarily for walking purposes. From the selection of walking knees, the amputee engaged in athletic activities must compromise performance and durability of the knee. 
     SUMMARY 
     Under the embodiments of the invention, the prosthetic knee is designed to be used to deliver security and stability to amputees, particularly high activity amputees engaged in athletic activities, particularly sprinting or running. 
     The prosthetic knee is a multi-axial knee having stability adjustment to optimize the balance between knee stability and dynamic behavior for each individual user. The prosthetic knee allows for prevention of long term injury and discomfort, and facilitates improved gait characteristics to improve sprinting and running performance. 
     According to an embodiment, a prosthetic knee has a vertical axis, a locking head aligned to the vertical axis, a chassis extending obliquely relative to the vertical axis, and a plurality of links connecting the locking head to the chassis. The knee preferably has a four-bar geometry defined at least in part by the plurality of links for improved ground clearance. 
     The prosthetic knee has a swing control mechanism to control the flexion angle of a knee. The swing control mechanism includes a flexion stop connected to the chassis and extending outwardly from the chassis and obliquely relative to the vertical axis. The flexion stop may extend obliquely relative to the vertical axis at least by 90 degrees. The flexion stop is preferably a spring having a segment defining a generally flat surface. 
     The flexion stop is intended to stop the flexion of the knee by impacting on a prosthetic socket. The energy from the flexion (bending of the knee), the angular kinetic energy from a shank portion of the prosthesis is stored in the flexion stop, providing a powerful and fast extension of the shank portion, thus facilitating sprinting and running. The impact on the socket provides feedback to the user about the location of the prosthetic foot. 
     The prosthetic knee may include a bracket adjustably secured to the chassis and relative to the vertical axis, and the flexion stop is mounted to the bracket. The bracket defines at least one arcuate slot, and is adjustable relative to the chassis by the arcuate slot. The prosthetic knee may further include a fastener secured to the bracket at an angle relative to the chassis. The bracket is preferably adjustable to the vertical axis generally within the range of 0-30 degrees. 
     The chassis preferably defines a flat mounting surface extending obliquely relative to the vertical axis. The mounting surface extends relative to the vertical axis generally within the range of 10 to 35 degrees. 
     A mounting plate may be movably secured to the mounting surface by at least one fastener, without the necessity or inclusion of the bracket. 
     When starting a sprint in a competition, sprinters often use starting blocks where both knees are usually in a flexed position. Prosthetic knees used for sprinting are typically not load bearing in a flexed position, which means that so an amputee sprinter may get no forward propulsion from the prosthetic leg when pushing out of a starting block. To address this situation, the prosthetic knee may include a block lock. The block lock is manually activated to allow for load bearing in a flexed position which becomes inactive after one activation cycle of the runner (i.e., disengage when the knee is extended as the sprinter comes out of the starting block). 
     According to an embodiment of a block lock, the block lock has a spring loaded tab block preventing movement of a rear link when engaged therewith in flexion position. The tab block arranged to be pulled by the spring as the knee enters into extension and remain retracted to disengage from the rear link. 
     The prosthetic knee may include a housing and an eccentric friction brake including a friction shaft having an eccentric profile rotating in the housing as the knee rotates at an upper pivot point. A friction pad presses against the friction shaft, and is controlled by a spring element connected to the friction pad by a ball and a guide block. A friction screw allows for adjustment of preloading the spring element. As the friction shaft rotates, eccentricity of the friction shaft is arranged to change position relative to the other parts of the friction brake and compresses the spring element to increase a friction force on the friction shaft, and slow down rotation of the knee just before full extension is reached, without changing the rest of the swing phase of the knee. 
     To provide the user with information about the location of the rotation of the knee, an audio feedback mechanism is attached to a pivot axis of the prosthetic, and provides an audible sound as the knee rotates. 
     A prosthetic knee kit, includes a prosthetic knee having a vertical axis, and includes a locking head aligned to the vertical axis, a chassis extending obliquely relative to the vertical axis, a plurality of links connecting the locking head to the chassis. The kit has a plurality of flexion stops arranged to be connected to the chassis and extending outwardly from the chassis and obliquely relative to the vertical axis. Each of the flexion stops is arranged to be connected to the chassis at a plurality of different angles relative to the vertical axis. 
     The prosthetic knee may be equipped with an extension lock that provides stability and locking of the prosthetic knee in an extension position. Locking in an extension position may be beneficial in certain circumstances such as in running when there is an onset of runner fatigue in long distance running. 
     According to an embodiment of the extension lock, an arm is pivotally connected to the housing and arranged to engage a notch formed on at least one of the links. The extension lock may include first and second arms secured to one another by a handle bar. Tips of the first and second arms are configured to engage the first and second links, respectively. The notch may be formed on the links proximate to the housing. 
     When locking the prosthetic knee in an extension position, the handle bar is pushed upwardly so as to draw an arm segment into and make it engage notches formed by the links, which prevents further rotation of the links relative to the housing. The prosthetic knee may be unlocked by pulling the handle bar downwardly which draws the arm segment out from the notches. The extension lock may be retained in the disengaged configuration so as not to interfere with flexion and extension of the prosthetic knee, and is only selectively placed into the engaged, locked configuration when desired. The extension lock may be configured to operate in directions or movements different from those discussed above, such as by a reversal of directional movement. A spring may bias the handle bar so that it is maintained in the disengaged configuration. 
     The numerous other advantages, features and functions of embodiments of a prosthetic knee are readily apparent and better understood in view of the following description and accompanying drawings. The following description is not intended to limit the scope of the prosthetic knee, but instead merely provides exemplary embodiments for ease of understanding. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood regarding the following description, appended claims, and accompanying drawings where: 
         FIG. 1  is an assembly view showing a prosthetic leg assembly including a prosthetic knee. 
         FIG. 2  is a perspective view of an embodiment of a prosthetic knee. 
         FIG. 3  is a cross-sectional elevational view of the prosthetic knee taken along line III-III in  FIG. 2 . 
         FIG. 4  is an elevational view of another embodiment of a prosthetic knee showing dimensions of various components. 
         FIG. 5  is the elevational view of  FIG. 4  and shows spatial relationships among the components. 
         FIG. 6  is a cross-sectional elevational view showing an extension stop in a first position. 
         FIG. 7  is a cross-sectional elevational view showing the extension stop of  FIG. 6  in a second position. 
         FIG. 8  is a sectional view of the prosthetic knee of  FIG. 5  in a prosthetic leg assembly in a flexion configuration wherein the brake is in a blocked position. 
         FIG. 9  is a sectional view of the prosthetic knee of  FIG. 5  in a prosthetic leg assembly in an extension configuration wherein the brake is in an unblocked position. 
         FIG. 10  is a sectional view of the prosthetic knee of  FIG. 5  in a prosthetic leg assembly in a flexion configuration wherein the brake is in an unblocked position. 
         FIG. 11  is a sectional view of the prosthetic knee in a prosthetic leg assembly in a flexion configuration wherein a variation of a brake is in a blocked position. 
         FIG. 12  is a sectional view of the prosthetic knee in a prosthetic leg assembly in an extension configuration wherein the brake of  FIG. 11  is in an unblocked position. 
         FIG. 13  is a sectional view of the prosthetic knee in a prosthetic leg assembly in a flexion configuration wherein the brake of  FIG. 11  is in an unblocked position. 
         FIG. 14  is an embodiment of an audio feedback mechanism. 
         FIG. 15  is an elevational side view of a prosthetic knee embodiment having swing control adjustability. 
         FIG. 16  is an elevational frontal view of the prosthetic knee embodiment of  FIG. 15 . 
         FIG. 17  is a perspective view of the prosthetic knee embodiment of  FIG. 15 . 
         FIG. 18  is an elevational side view of a prosthetic knee embodiment having an extension lock in an engaged position. 
         FIG. 19  is a sectional plan view of the prosthetic knee embodiment of  FIG. 18 . 
         FIG. 20  is a sectional side view of the prosthetic knee embodiment of  FIG. 18  in extension with the extension lock in a disengaged position. 
         FIG. 21  is a sectional side view of the prosthetic knee embodiment of  FIG. 18  in flexion with the extension lock in a disengaged position. 
     
    
    
     The drawing figures are not necessarily drawn to scale, but instead are drawn to provide a better understanding of the components, and are not intended to be limiting in scope, but rather to provide exemplary illustrations. The figures illustrate exemplary embodiments of a prosthetic knee and the components, and in no way limit the structures or configurations of a prosthetic knee and components according to the present disclosure. 
     DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS 
     A. Environment and Context 
     To understand the operation of the prosthetic knee described, a basic discussion of the gait cycle is required. A gait cycle defines the movement of the leg between successive heel contacts of the same foot. The gait cycle has two phases: stance and swing. The stance phase has three time periods: heel-strike, mid-stance and toe-off. 
     During mid-stance, the knee joint will be at full extension. An actual knee joint will have some flexion between heel-strike and mid-stance and between mid-stance and toe-off. This is called “stance flexion.” Not all prosthetic joints provide for stance flexion, and for those that do, they are mechanically complex, expensive, or both. These prosthetic joints typically require frequent maintenance and replacement. The amount of stance flexion required can vary from user to user, while most prosthetic joints have no adjustability. 
     Maximum flexion of the knee joint, while walking, will occur at the end of the toe-off phase. The maximum flexion is typically determined in part by the speed at which a person is walking. The faster a person walks, the greater the maximum flexion, while the slower a person walks, the lesser the maximum flexion. In a natural knee, the maximum flexion can be controlled and limited via the musculature of the leg. In a prosthetic knee joint, some artificial means of controlling and limiting the maximum flexion is typically provided. Immediately following the end of the toe-off phase begins the swing phase. 
     While the stance phase has three time periods, the swing phase has two time periods: acceleration and deceleration. The acceleration phase begins immediately following the maximum flexion during the toe-off phase. During the acceleration phase, the lower portion of the leg, comprising the shin and foot, swings back towards full extension. In a natural knee joint, a deceleration phase follows the acceleration phase, during which the lower portion of the leg continues to swing towards full extension. Some prosthetic joints do not provide for any deceleration during the swing phase. Other prosthetic joints provide deceleration by using costly and bulky hydraulic or pneumatic cylinders. The deceleration required can vary from user to user, while most prosthetic joints have no adjustability. 
     For further ease of understanding the joint disclosed, a description of a few terms is necessary. As used, the term “upper” has its ordinary meaning and refers to a location above, or higher than another location. Likewise, the term “lower” has its ordinary meaning and refers to a location below, or underneath another location. The term “rear” is used interchangeably with the term “posterior,” and also has its ordinary meaning and refers to a location that is behind or to the rear of another location. The term “front” is used interchangeably with the term “anterior,” and has its ordinary meaning and refers to a location that is ahead or to the front of another location. 
     B. Exemplary Embodiments 
       FIG. 1  illustrates the general configuration of a prosthetic leg assembly  1  for an above-the-knee or transfemoral amputee. The leg assembly  1  includes a prosthetic knee  10 , a socket  14  connected to the knee  10  and arranged to receive the residual limb, and a prosthetic foot  12 . 
     The emphasis of this disclosure is on the prosthetic knee. The socket may be constructed and configured under any known methods and structures described in at least U.S. Pat. No. 7,438,843, granted Oct. 21, 2008, and incorporated by reference. An exemplary foot, such as the one depicted in  FIG. 1 , may be the CHEETAH foot sold by Ossur hf of Reykjavik, Iceland, and a “running foot.” 
     An exemplary embodiment of a prosthetic knee  10  is shown in  FIGS. 2 and 3 . As shown, the prosthetic knee includes a housing  24 , parallel front links  18 ,  20 , a rear link  22 , and a chassis  16 . The prosthetic knee  10  includes a locking head  26 , in the preferable form of a pyramid adapter, at the top and a distal mounting surface  34 . The front links and the rear link may be constructed under the prosthetic knee described in co-pending U.S. provisional application No. 61/491,707, filed on May 31, 2011. 
     The front links  18 ,  20  are oriented, sized and located to provide for stability. The front links  18 ,  20  are on and pivotally connected to opposed sides of the chassis  16  and the housing  24 , and pivot at upper and lower pivot points  28 ,  30 . The rear link  22  pivotally connects to a housing flange  27  extending posteriorly from the housing  24  and to the chassis  16 , and pivots at upper and lower pivot points  32 ,  33 . 
     Of particular note, the front links  18 ,  20  both extend above the rear link  22  and substantially below the rear link  22 . However, the front links  18 ,  20  are not too long for this leads to poor torsion whereas the front links  18 ,  20  are not too short for this makes it difficult to fit the prosthetic knee  10 . 
     Besides the selection of the length of the links as parameters for designing the knee, both the flexion factor (i.e., large angle of locking and easy swing initiation) and a large flexion angle which allows for adapter clearance at 130 and 140 degrees are considered. Additional parameters include locating the links for the greatest toe clearance, good stability, ease of swing initiation, and good maximum flexion for both the clamp attachment and pyramid adapter. 
     The mounting surface  34  is arranged for securing directly to the running foot configured for running which often connect to a knee via a pylon and ankle apparatus. The mounting surface  34  is preferably flat, and is arranged at an oblique angle relative to a vertical axis A-A. The angle of the mounting surface relative to a vertical axis may be 15 to 25 degrees. The running foot may be secured to the mounting surface  34  by a plurality of fasteners (not shown) received in openings  42  located along the mounting surface  34 . 
     A flexion stop  38  is mounted on a bracket  36  that is adjustably secured to the chassis  16 . The flexion stop  38  is arranged to stop the flexion of the knee by impacting the socket. Angular kinetic energy from the flexion or bending of the knee is stored in the flexion stop, urging the knee into a powerful and fast extension to facilitate sprinting or running. The impact of the flexion stop on the prosthetic socket provides feedback to the user about the location of the prosthetic foot. 
     According to this variation, the bracket  36  is adjustably arranged relative to the chassis  16 , and hence the flexion stop  38 , with at least one arcuate slot  40  on opposed sides of the bracket  36 . The angle of the flexion stop  38  relative to a vertical axis A-A can be adjusted accordingly by tightening the bracket  36  along the at least one slot  40  to the chassis  16  by suitable fasteners. A preferable range of adjustment corresponding to the slots is about 0-25 degrees from the vertical axis. The flexion stop  38  can be secured to the bracket  36  along a generally flat surface  44 . 
     According to this embodiment, the flexion stop is constructed from a carbon fiber spring, although other materials may be employed such as polymers and composites. To prevent damage of the flexion stop or the prosthetic socket, a pad of cushioning material may be adhered to the end of the flexion stop or the prosthetic socket. As depicted in  FIG. 3 , the flexion stop may be elongate and define a compound curve, although other configurations are possible such as straight or curved, or a combination of the same. 
     In reference to  FIGS. 4 and 5 , an embodiment of the prosthetic knee is shown having a different flexion stop and means for attachment.  FIG. 4  illustrates a flexion stop  54  having a plurality of predetermined configurations  54 A- 54 C which permit the user to select which of the configurations  54 A- 54 C to use. The configurations  54 A- 54 C are arranged at different angles relative to the vertical axis A-A. The flexion stops  54 A- 54 C are arranged incrementally at angles 100-120 degrees respectively relative to the vertical axis A-A. 
     Unlike in the embodiment of  FIGS. 2-3 , the attachment variation in  FIG. 4  does not include variable adjustment, in part in view of the selection of different flexion stops, and includes a plate  56  secured to the mounting surface  34  by a plurality of fasteners  58 . 
     Regarding the spatial relationship among the components of the prosthetic knee,  FIGS. 4 and 5  show the ranges of various ratios of locations among the pivot points  28 ,  30 , and  32 ,  33  and the lengths of the links relative to one another, taking 1.0 as the base number. Particularly, the relative locations of the links and their positions relative to attachments in the form of the pyramid adapter and the clamp attachment determine their geometry and spatial relationships. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Dimension 
                 Ratio 
               
               
                   
                   
               
             
            
               
                   
                 A 
                 7.3-7.7 
               
               
                   
                 B 
                 3.5-3.9 
               
               
                   
                 C 
                 2.0-2.2 
               
               
                   
                 D 
                 4.0-4.4 
               
               
                   
                 E 
                 0.8-0.9 
               
               
                   
                 F 
                 1.85-2.05 
               
               
                   
                 G 
                 1.2-1.4 
               
               
                   
                 H 
                 7.0-7.4 
               
               
                   
                 I 
                  1.2-1.35 
               
               
                   
                 J 
                 1.85-2.05 
               
               
                   
                   
               
            
           
         
       
     
     Because the prosthetic knee is arranged for sprinting or running, the linkage lengths and locations of the pivots are selected considering there is no heel strike, since at least the running foot does not have a heel, as compared with conventional prosthetic feet. In conventional feet, the linkage lengths and the pivot points are selected for stability at heel strike while maintaining a relatively easy release at flexion at late stance or toe off. In a prosthetic knee arranged for sprinting or running, stability is of less concern since many athletes have powerful hips which enable them to actively stabilize the knee joint as required. 
     Certain parameters to consider include ground clearance with mid swing shortening due to the geometry of the prosthetic assembly. Another parameter includes a large range-of-motion in the knee since many runners flex their knee up to 150 degrees. A low overall height is of concern for the knee since running feet are long, and should fit on short amputees. Parallel vertical linkages should be avoided or minimized since if the front links and the rear link reach a position where they are parallel, the instantaneous center of rotation shifts from being far above the knee to being far below the knee. This can cause an undesirable significant jolt or impact on the residual limb (referred as “terminal impact”) at high running speeds. 
     1. Swing Control Mechanisms 
     The prosthetic knee has a variety of swing control mechanisms that allow for control of both extension and flexion of the prosthetic knee. 
     The flexion stop  38  is provided to control the flexion angle of the prosthetic knee, and operates by controlling flexion by adjustment of the angle the flexion stop is mounted to the chassis. The flexion stop also provides extension assist by having stored energy upon impact by the prosthetic socket, which urges the knee away from the prosthetic socket into extension. 
     In reference to  FIG. 3 , the prosthetic knee also includes an extension assist mechanism  19 . The extension assist mechanism includes the extension assist piston  46 , which is retained in an inner housing  48 , which remains fixed, with an extension assist spring. Seals, such as O-rings, are provided between the external surface of the extension assist piston  46  and the internal surface of the inner housing  48 . 
     The upper end of the inner housing  48  is held in a first hole in the chassis  16  between the upwardly extending flanges, so the extension assist piston  46  can be biased into engagement with the lower end  49  of the rear link  22 , as discussed below. 
     An adjustable external housing  47  is positioned within the chassis  16 , and is provided coaxially with the inner housing  48 , and receiving the inner housing  48  (and the extension assist piston  46 ) with the seal located therebetween, and a spring guide and the extension assist spring. The spring guide engages a bottom end of the extension assist spring, and the upper end of the extension assist spring engages a bottom end of the extension assist piston  46 . 
     By accessing the adjustable external housing  47 , a clinician can rotate the adjustable external housing  47  in a vertical direction (upwards or downwards) to alter the compression of the extension assist spring, and alter the biasing force applied to the extension assist piston  46  by the extension assist spring, and therefore the biasing force applied to the rear link  22  by the extension assist piston  46 . In this manner, the extension assist mechanism allows for adjustment to the individual user&#39;s speed, by adjusting the outer housing. 
     As also shown in  FIG. 3  and described in U.S. provisional application No. 61/491,707, the prosthetic knee also includes an extension stop  50  which further limits extension of the knee. The extension stop  50  includes a stability adjustment screw connected to a bumper  51  which is struck a raised surface  53  on the rear link  22 . The extension stop  50  balances between stability and dynamic behavior of the prosthetic knee. It allows the clinician to match the prosthetic knee to the needs and behavior of the wearer by tightening or loosening the stability adjustment screw, which alters the position of the bumper. 
     The extension stop prevents further extension of the knee. When the knee reaches full extension, the user can feel the terminal impact through the prosthetic socket. While the terminal impact provides the user tangible feedback, it should be dampened to prevent long term injury or discomfort to the user, and facilitate improved gait characteristics to improve sprinting or running. 
     Besides the aforementioned extension stop, other devices may be used alone or in combination with one another to handle terminal impact. The prosthetic knee may be provided with a hydraulic damper, a double durometer bumper besides the bumper  51  which may be on the rear link, a constant friction brake mechanism as described in U.S. provisional application No. 61/491,707, or an eccentric friction brake. 
       FIGS. 6-7  depict an embodiment of an eccentric friction brake  52 . A friction shaft  66  having an eccentric profile rotates in the housing  24  as the knee rotates at the upper pivot point  28 . A friction pad  68  presses against the friction shaft  66 , and is controlled by a spring element  72 , such as at least one disc spring, which is connected to the friction pad  68  by a ball  76  and a guide block  70 . A friction screw  74  allows for adjustment of preloading the spring element  72 . 
     In operation, as the friction shaft  66  rotates, the eccentricity of the shaft changes position relative to the other parts of the friction brake and compresses the spring element  72 , as evidenced by the different dimensions M and N between the friction screw  74  and the guide block  70  in  FIGS. 6 and 7 . This results in an increase in force exerted on the friction pad  68 , and increases the friction force on the friction shaft  66 , slowing down the rotation of the knee just before full extension is reached, without changing the rest of the swing phase of the knee. 
     In a variation of the friction brake, a hydraulic fluid may replace the spring element, and provides increased ability to control the extension of the knee separately. 
     2. Block Mechanism 
     When a sprinter starts in a competition, a starting block is typically used. When in position with the starting blocks, both knees are in a flexed position. Since prosthetic knees used for sprinting are not configured for load-bearing in a flexed position, an amputee sprinter has no forward propulsion from the prosthetic leg when initially pushing from the starting block. The block mechanism must become inactive after the initial push off from the starting blocks and remain disengaged from the housing so as not to interfere with further use of the knee during the sprint. 
     In  FIGS. 8-13 , two block mechanisms are shown for providing the initial assist only required at the initial push off from the starting blocks. 
     In observing  FIGS. 8-10 , a block mechanism in the form of a pivotable blade block  60  is manually arranged to block movement of the housing relative to the chassis, and maintain the knee in a flexed position, as shown in  FIG. 8 . Upon initial push off from the starting blocks, the blade block  60  is released from locking the housing relative to the chassis, as shown in  FIG. 9  wherein the leg is in extension. A spring (not shown) may assist placing the blade lock away from the housing and chassis.  FIG. 10  shows the knee as it is in flexion subsequent to the initial push off wherein the blade lock  60  is maintained from engaging the housing. 
     In another embodiment of the block mechanism,  FIG. 11  depicts a tab block  62  which prevents movement of the rear link  22  when engaged therewith. When the knee extends, as shown in  FIG. 12 , a spring  64  pulls the tab block  62  toward a front side  63  of the chassis. When the knee goes back into flexion, as illustrated in  FIG. 13 , the tab block  62  remains completely disengaged from the rear link  22 . 
     3. Audible Feedback Mechanism 
     An audio feedback mechanism may provide the user with information about the location of the rotations of the prosthesis. As illustrated in  FIG. 14 , an audible feedback embodiment includes a gear wheel  78  attached to one of the pivot axes of the knee. A spring loaded pin  80  is fixed to another structural part of the knee and engages the gear wheel  78  as the gear wheel  78  rotates in relation to the pin  80 . During this rotation, an audible sound is produced. 
     The audible sound changes in frequency with the speed of the knee and a notable change in pitch is observed as the knee changes in rotational direction. This allows the user to get a better feeling for the location and/or speed of the shank in space improving performance and safety. Other mechanisms may also be used for providing position, velocity or acceleration related feedback to the user. 
     4. Swing Control Adjustability 
     The prosthetic knee embodiment  100  according to  FIGS. 15-17  has swing control adjustability in the housing  102 . As with the embodiment of  FIG. 2 , the prosthetic knee  100  includes a chassis  16 , front links  18 ,  20 , and a rear link  22 . 
     The swing control adjustability features of the prosthetic knee  100  are similar to the swing control adjustability features provided in the prosthetic knee products offered by Ossur hf of Reykjavik, Iceland, and having product names TOTAL KNEE 1900, TOTAL KNEE 2000 and TOTAL KNEE 2100. Although the prosthetic knee embodiment includes swing control adjustability features, they are configured for running or elevated uses above normal walking, and are in combination with other features of the prosthetic knee embodiments discussed. 
     According to the prosthetic knee  100 , the rear link  22  has bumpers  104  adapted to strike an undersurface of the housing  102 . The bumpers  104  minimize any shock incurred during extension of the prosthetic knee, and protect the housing  102  from damage. 
     Regarding swing control adjustability, the housing  102  defines hydraulic resistance adjustability by way of a plurality of valves  106 ,  108 ,  110 . The first valve  106  is arranged to control flexion resistance from 60 degrees to a full or complete flexion position. The second valve  108  is arranged to control resistance from full extension to 60 degrees (0-60). The third valve  110  may be on an opposite side of the first and second valves  106 ,  108 . The third valve  110  controls extension resistance. If the third valve  110  is turned clockwise, the valve is closed which increases resistance; if the third valve  110  is turned counterclockwise, the valve is opened which decreases resistance. 
     A friction adjustment valve and screw  112  may also be used in combination with the other swing control adjustability features. The friction adjustment valve and screw  112  allows for adjustment to increase or decrease friction with an elastic polymer medium, so the swing phase of the prosthetic knee  100  is controlled and steady. 
     The prosthetic knee  100  may also include an extension promoter  114  provided to reduce excessive heel rise. Clockwise rotation decreases heel rise, whereas counterclockwise rotation increases heel rise (when already having been decreased). 
     Each of these swing control adjustability features is arranged in a manner to withstand the rigors of active amputees, including intense athletic activities. The valves are provided with increased fluid capacity over known models to better resist flexion and control swing. The valves may likewise be relocated over known prosthetic knees to accommodate the larger valves and increased fluid capacity. The prosthetic knee  100  may include fins  116  to cool the knee due to the resistance which occurs by the increased valve size. 
     5. Extension Lock 
       FIGS. 18-21  show a prosthetic knee embodiment  118  sharing certain features with the prosthetic knee  100 , and including upper and lower pyramid adapters  26 ,  120  and an extension lock  124 . In this embodiment, the foot connection has the lower pyramid adapter  120  which replaces the direct connection shown in the embodiments associated with  FIG. 13 . The flexion stop  54  may be directly connected to an inclined surface  122  of the rear link  22 . 
     The extension lock  124  pivotally connects to the housing  102  and engages notches  132  formed on the front links  18 ,  20 . The extension lock  124  includes a first arm segment  126  pivotally attached to the housing  102  by a fastener  128  which permits a second arm segment  130  to engage or disengage with the notch  132 . Each side or arm of the extension lock  124  corresponds to the front links  18 ,  20 , respectively, and these sides are connected by an elongate handle bar  134  located on the front of the prosthetic knee. A tip  136  of the second arm segment has a complementary shape to the notch  132  so as to assure engagement and retention with the notch  132 . 
       FIG. 18  shows the prosthetic knee  118  in an extension configuration with the extension lock  124  engaging the front links  18 ,  20 . This may be accomplished by pulling the handle bar  134  upwards U which in turn draws the second arm segment  130  downwards to engage the notch  132 . Once engaged, the second arm segment rests within the notch, thereby preventing rotation and maintaining the prosthetic knee in extension. 
       FIG. 20  illustrates the prosthetic knee  118  with the extension lock  124  disengaged from the front links  18 ,  20 , thereby permitting rotation or flexion of the prosthetic knee. This is accomplished by pulling downwardly on the handle bar which draws the second arm segment out from the notch.  FIG. 21  depicts the prosthetic knee  118  in flexion with the extension lock  124  fully disengaged. When disengaged, the prosthetic knee can rotate back and forth from flexion and extension without interference from the extension lock  124 . 
     A spring arrangement  138  is arranged to bias the extension lock  124  in the disengaged position so as to avoid interference with movement of the links. The handle bar  134  may be pushed upwardly against resistance from the spring to place the tip  136  in the notch  132 , and allow the tip  136  to maintain engagement with the notch  132  when the prosthetic knee is in the extension configuration. 
       FIGS. 20 and 21  depict a torsion spring  138  that wraps about or engages the handle bar and biases against the housing  102 . Alternative spring arrangements may be employed such as a clip configuration engaging at least part of the handle bar and biasing against the housing, or a flat, leaf biasing against the handle bar and the housing. The springs may be constructed from a variety of materials, and the handle bar and/or housing may be adapted with notches or grooves to retain the spring. 
     Not necessarily all such objects or advantages may be achieved under any embodiment of the invention. For example, those skilled in the art will recognize that the invention may be embodied or carried out to achieve or optimize one advantage or group of advantages as taught without achieving other objects or advantages as taught or suggested. 
     The skilled artisan will recognize the interchangeability of various components from different embodiments described. Besides the variations described, other known equivalents for each feature can be mixed and matched by one of ordinary skill in this art to construct an orthopedic device under principles of the present invention. Therefore, the embodiments described may be adapted to orthopedic systems for securing, supporting or comforting limbs or other anatomy. 
     Although this invention has been disclosed in certain preferred embodiments and examples, it therefore will be understood by those skilled in the art that the present invention extends beyond the disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents. It is intended that the scope of the present invention disclosed should not be limited by the disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.