Abstract:
Implant apparatus and methods directed toward treating conditions involving the knee joint and the patella specifically are disclosed. Full range of motion of the knee joint and tissue integrity are maintained in treatment approaches involving implanting a joint surface load reducing implant proximate the joint to change the direction of the tendons or muscles exerting forces on the joints.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/568,615 filed Dec. 8, 2011, which is entirely incorporated herein by reference. 
     
    
     BACKGROUND OF THE DISCLOSURE 
       [0002]    The present disclosure is directed towards systems and methods for treating tissue of a body and more particularly, towards approaches designed to treat a natural joint and conditions involving the patella specifically. 
         [0003]    A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally. Structural classification is determined by how the bones connected to each other, while functional classification is determined by the degree of movement between the articulating bones. In practice, there is significant overlap between the two types of classifications. 
         [0004]    There are three structural classifications of joints, namely fibrous or immovable joints, cartilaginous joints and synovial joints. Fibrous/Immovable bones are connected by dense connective tissue, consisting mainly of collagen. The fibrous joints are further divided into three types: sutures which are found between bones of the skull; syndesmosis which are found between long bones of the body; and gomphosis which is a joint between the root of a tooth and the sockets in the maxilla or mandible. 
         [0005]    Cartilaginous bones are connected entirely by cartilage (also known as “synchondroses”). Cartilaginous joints allow more movement between bones than a fibrous joint but less than the highly mobile synovial joint. Synovial joints have a space between the articulating bones for synovial fluid. This classification contains joints that are the most mobile of the three, and includes the knee and shoulder. These are further classified into ball and socket joints, condyloid joints, saddle joints, hinge joints, pivot joints, and gliding joints. 
         [0006]    Joints can also be classified functionally, by the degree of mobility they allow. Synarthrosis joints permit little or no mobility. They can be categorized by how the two bones are joined together. That is, synchrondoses are joints where the two bones are connected by a piece of cartilage. Synostoses are where two bones that are initially separated eventually fuse together as a child approaches adulthood. By contrast, amphiarthrosis joints permit slight mobility. The two bone surfaces at the joint are both covered in hyaline cartilage and joined by strands of fibrocartilage. Most amphiarthrosis joints are cartilaginous. 
         [0007]    Finally, diarthrosis joints permit a variety of movements (e.g. flexion, adduction, and pronation). Only synovial joints are diarthrodial and they can be divided into six classes: 1. ball and socket—such as the shoulder or the hip and femur; 2. Hinge—such as the elbow; 3. Pivot—such as the radius and ulna; 4. condyloidal (or ellipsoidal)—such as the wrist between radius and carps, or knee; 5. Saddle—such as the joint between carpal thumbs and metacarpals; and 6. Gliding—such as between the carpals. 
         [0008]    Synovial joints (or diarthroses, or diarthroidal joints) are the most common and most moveable type of joints in the body. As with all other joints in the body, synovial joints achieve movement at the point of contact of the articulating bones. Structural and functional differences distinguish the synovial joints from the two other types of joints in the body, with the main structural difference being the existence of a cavity between the articulating bones and the occupation of a fluid in that cavity which aids movement. The whole of a diarthrosis is contained by a ligamentous sac, the joint capsule or articular capsule. The surfaces of the two bones at the joint are covered in cartilage. The thickness of the cartilage varies with each joint, and sometimes may be of uneven thickness. Articular cartilage is multi-layered. A thin superficial layer provides a smooth surface for the two bones to slide against each other. Of all the layers, it has the highest concentration of collagen and the lowest concentration of proteoglycans, making it very resistant to shear stresses. Deeper than that is an intermediate layer, which is mechanically designed to absorb shocks and distribute the load efficiently. The deepest layer is highly calcified, and anchors the articular cartilage to the bone. In joints where the two surfaces do not fit snugly together, a meniscus or multiple folds of fibro-cartilage within the joint correct the fit, ensuring stability and the optimal distribution of load forces. The synovium is a membrane that covers all the non-cartilaginous surfaces within the joint capsule. It secretes synovial fluid into the joint, which nourishes and lubricates the articular cartilage. The synovium is separated from the capsule by a layer of cellular tissue that contains blood vessels and nerves. 
         [0009]    Various maladies can affect the joints, one of which is arthritis. Arthritis is a group of conditions where there is damage caused to the joints of the body. Arthritis is the leading cause of disability in people over the age of 65. 
         [0010]    There are many forms of arthritis, each of which has a different cause. Rheumatoid arthritis and psoriatic arthritis are autoimmune diseases in which the body is attacking itself. Septic arthritis is caused by joint infection. Gouty arthritis is caused by deposition of uric acid crystals in the joint that results in subsequent inflammation. The most common form of arthritis, osteoarthritis is also known as degenerative joint disease and occurs following trauma to the joint, following an infection of the joint or simply as a result of aging. 
         [0011]    Unfortunately, all arthritides feature pain. Patterns of pain differ among the arthritides and the location. Rheumatoid arthritis is generally worse in the morning; in the early stages, patients often do not have symptoms following their morning shower. 
         [0012]    Maladies that can affect the knee joint specifically include patellar or kneecap pain, misalignment or dislocation. Pain can exist when there is an excess of force contact between the patella and femur. This can be due to misalignment associated arthritis or anatomical conditions specific to an individual. Kneecap dislocation occurs when the triangle-shaped patellar bone covering the knee moves or slides out of place. This problem usually occurs toward the outside of the leg and can be the result of patella misalignment due to patient specific anatomy or osteoarthritis, or from trauma. 
         [0013]    The patella rests in the patellofemoral groove, a cavity located on the knee between the distal femur and the tibia. The sides of the patella attach to certain ligaments and tendons to stabilize and support it. The upper border of the patella attaches to the common tendon of the quadriceps muscles. The side or medial borders of the patella are attached to the vastus medialis muscle, and the lower border of the patella is connected by the patellar ligament to the tibial tuberosity. The main ligament stabilizer, the patellofemoral ligament, rests directly over the femur and the patella while the lateral and medial collateral ligaments acts as the secondary ligament stabilizers from either side of the patella. 
         [0014]    Arthritis of the patella is one of the many causes of knee pain. Patella femoral arthritis, is identified when loss of cartilage behind the patella leads to pain in the knee. The pain typically worsens when a patient walks hills, goes up or down stairs, or does deep knee flexion. Arthritis of the patella can result from an injury to the knee joint, ordinary wear and tear, or most commonly the improper tracking of the patella on the femur when the patella does not line up properly. 
         [0015]    Non-surgical treatments for patella femoral arthritis include exercises, anti-inflammatory drugs, weight loss, pain medication and cortisone shots to help lessen the pain. External braces or taping to improve patella tracking can also be used. However, if sufficient bone loss occurs, surgery may be necessary. 
         [0016]    Surgical options include cartilage shaving, cartilage excision, drilling into subchondral bone to induce regeneration or a lateral release where a tendon is cut to help align the knee. Other surgical options include a tibial tuberosity osteotomy, partial knee replacement and a total knee replacement, or removal of the patella entirely. 
         [0017]    In a tibia tuberosity osteotomy, the bump on which your patellar tendon attaches (tibial tuberosity) is moved surgically by cutting the bone and adding plates and/or pins. The tibial tuberosity is moved up, down, left or right depending on the location of the damaged cartilage to move the load on the cartilage to a part of the knee that is still healthy—assuming there is such an area. 
         [0018]    In a patellectomy the patella is removed outright. Sometimes this works, but sometimes removing the patella may hasten the onset of arthritis in the rest of the knee. A patella replacement may also be performed where part or all of the patella is replaced with an implant. 
         [0019]    Recently, less conventional approaches to treating the patella have been proposed. In one approach, a patellar implant is placed below a patellar tendon to elevate or tilt the patellar tendon. This consequently may alter patellar tracking and decrease forces on the patella to thereby alleviate pain caused by the patella contacting the femur or tibia or by decreasing force loads across the patella-femoral joint. 
         [0020]    In a related approach, improper force distributions associated with the patella are addressed by displacing tissues in order to realign force vectors and alter movement across loading the knee joint. Here, again, an objective is to lessen the force with which the patella is pressed against the femur during the gait cycle. 
         [0021]    Sufficient attention does not appear to have been given in prior patella treatment approaches, however, to treatment of the knee joint throughout its full range of motion. There is also a need for avoiding negative remodeling of the patellar ligament as well as approaches to maintain a desired alignment of an implant and target tissue. 
         [0022]    Therefore, what is needed and heretofore lacking in prior attempts to treat joint pain associated with patella misalignment or dislocation is an implantation method and implant device which addresses full range of joint movement, and which maintains desired structural integrity of anatomy forming the knee joint. 
         [0023]    The present disclosure addresses these and other needs. 
       SUMMARY 
       [0024]    Briefly and in general terms, the present disclosure is directed towards treating joint structures. In one aspect, there are disclosed approaches to redistributing forces of the patella to alleviate pain or to address misalignment. 
         [0025]    In one particular embodiment, there is provided an implant which is contoured to receive the patellar tendon. The contour of the implant is configured to define structure preventing the patellar tendon from disengaging from the implant during a full range of motion of a knee joint. The implant is also contoured to avoid negative remodeling of the tissue of the knee. 
         [0026]    In one embodiment, an implant for decreasing pain caused by misalignment of bones at a joint includes an implant body configured to be implanted beneath a tendon. The implant has a smooth upper surface for allowing a tendon to slide over the implant body during articulation of the joint and a hook shaped portion configured to receive at least a portion of the tendon within an overhang of the hook to alter the tracking of the bones of the joint and alleviate pain associated with misalignment of the bones of the joint. 
         [0027]    In one embodiment of a method for treating a knee joint suffering from pain, the method includes the steps of inserting an implant below a patellar tendon; and configuring the implant so that it engages the patellar tendon throughout a full range of motion of the knee joint and so as to cause tension redistribution and contact force manipulation to alleviate pain. 
         [0028]    In another embodiment of a method for treating a knee joint suffering from pain, the method includes the steps of inserting an implant below a quadriceps muscle or quadriceps tendon; fixing the implant to the femur; configuring the implant so that it engages the quadriceps muscle or quadriceps tendon throughout a range of motion of the knee joint; and reducing compressive loads between the patella and femur with the implant. 
         [0029]    In another embodiment of a method for decreasing a force applied between two bones of a joint, the method includes the steps of affixing an implant to a tendon at a location between the tendon and a bone at a location proximate a the joint; allowing movement of the tendon and implant over the bone during articulation of the joint; and decreasing compressive loads between the two bones of the joint with the implant. 
         [0030]    The implant can embody a fluid filled bladder which self-contours to tissues. In one aspect, the implant can be adjustable through the movement, addition or removal of fluid. Various embodiments are contemplated to treat patellar misalignment and to inhibit dislocation, as well as to absorb loads applied by the patella upon adjacent anatomy. 
         [0031]    In a specific approach, an implant can include a two stage bladder having a main chamber for positioning under a ligament and a secondary chamber in communication with the main chamber. A valve can further be provided between the main and secondary chambers. During gait, fluid remains in the main chamber and performs ligament tensioning. During rest periods and when the limb is straight, fluid passes to the secondary chamber relieving tension on the ligament. This prevents negative remodeling or stretching of the ligament, as the same causes such therapy to become less effective over time. 
         [0032]    An implant can include a chamber that is fluid or gas filled to provide a compliant bolster and lengthening effect to increase a moment arm of the bolstered tendon or muscle. The chamber and bladder can be inflated or expanded over time to provide an increasing size or stiffness structure, or deflated or contracted to provide an opposite effect. A valve or injection port can be utilized for this functionality. 
         [0033]    The implant can further be configured such that when a leg is in extension, there is no force or little force in a first chamber of the implant. An elasticity of a second chamber is selected to cause fluid to flow into the first chamber. During gait, a valve between the chambers retains fluid within the first chamber. When at rest, with the joint in flexion the patella tendon presses fluid from the first chamber into the second chamber. 
         [0034]    In yet another approach, an implant is provided to treat a joint and functions to redistribute forces of a patella. The implant includes structure accomplishing attachment of the implant to the patella tendon. This implant can be a single spacer or can include one or more chambers that contain fluid or gas. Such an implant thus remains in place during a full range of motion of a knee joint. 
         [0035]    Other features and advantages of the present disclosure will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]      FIG. 1  is a front view, depicting an implant attached to members defining a joint according to an embodiment of the present disclosure; 
           [0037]      FIG. 2  is a cross-sectional view, depicting the structure of  FIG. 1  taken along line  2 - 2 ; 
           [0038]      FIGS. 3  is a perspective view, depicting the implant of  FIG. 1 ; 
           [0039]      FIGS. 4A and 4B  are side views, depicting a knee joint with and without tibial and femur implants; 
           [0040]      FIGS. 5A and 5B  are side views, depicting the knee joint and implants of  FIGS. 4A and 4B  with the joint flexed to about 30 degrees; 
           [0041]      FIGS. 6A and 6B  are side views, depicting the knee joint and implants of  FIGS. 4A and 4B  with the joint flexed to about 75 degrees; 
           [0042]      FIGS. 7A ,  7 B and  7 C are front views, depicting implants attached to members of a joint with a tibial implant only, a femoral implant only and both tibial and femoral implants according to an alternative example embodiments of the present disclosure; 
           [0043]      FIGS. 8A-8E  are front views, depicting implants having different shapes attached to a bone of a joint according to an alternative example embodiments of the present disclosure; 
           [0044]      FIGS. 9A-9D  are top views of implants having different shapes according to alternative embodiments of the present disclosure; 
           [0045]      FIGS. 10A-10C  are top views of implants having different inclinations of the superior surface according to alternative embodiments of the present disclosure; 
           [0046]      FIGS. 11A-11C  are top views of implants having different heights and different shapes according to alternative embodiments of the present disclosure; 
           [0047]      FIGS. 12A and 12B  are side views, depicting the knee joint and implants having different extensions with respect to the joint surfaces of  FIGS. 8B and 8C ; 
           [0048]      FIG. 13  is a front view, depicting an implant attached to members defining a joint according to alternative example embodiment of the present disclosure; 
           [0049]      FIG. 14  is a cross-sectional view, depicting the structure of  FIG. 1  taken along lines  5 - 5 ; 
           [0050]      FIG. 15  is yet another front view, depicting an implant attached to members defining a joint according to alternative embodiments of the present disclosure; 
           [0051]      FIG. 16  is a cross-sectional view, depicting the structure of  FIG. 1  taken along lines  7 - 7 ; 
           [0052]      FIG. 17  is a front perspective view depicting an implant with a roller according to an alternative embodiment of the present disclosure; 
           [0053]      FIG. 18  is a side cross-sectional view of the implant of  FIG. 17  with the knee joint at full extension; 
           [0054]      FIG. 19  is a side cross-sectional view of the implant of  FIG. 17  with the knee joint in flexion; 
           [0055]      FIG. 20  is cross-sectional view of the implant of  FIG. 17  taken along an axis of the roller; 
           [0056]      FIG. 21  is a side view, depicting an implant according to alternative embodiments of the present disclosure; 
           [0057]      FIGS. 22 and 23  are perspective views, depicting the implant of  FIG. 21 ; 
           [0058]      FIG. 24  is a front view, depicting an implant placed at a joint according to an alternative embodiment of the present disclosure; 
           [0059]      FIG. 25  is a front view, depicting a an implant placed at a joint according to an alternative embodiment of the present disclosure; and 
           [0060]      FIG. 26  is a cross-sectional view of an implant according to an alternative embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0061]    Referring now to the drawings, which are provided by way of example and not limitation, the present disclosure is directed towards apparatus and methods for treating a joint, and in particular, for treating a knee joint and for relieving pain caused by conditions involving the patella. Patella femoral osteoarthritis can be due to natural anatomy misalignment or can be a function of an earlier injury. Significant pain can be associated with these patellar conditions and can be a direct result of excessive forces being generated between the patella and adjacent anatomy. In particular, pain results when there are undesirable force contacts between the patella and the femur. The present disclosure is directed at alleviating pain by redirecting or absorbing excess forces without permanently remodeling tissues critical to the functioning of the knee joint. 
         [0062]    As shown in  FIGS. 1-3 , one approach to treating conditions involving a patella  90  can include the placement of an implant  100  at the knee joint  102 . The implant  100  can be generally U-shaped and can include terminal ends  104  configured to be affixed to body anatomy. In one approach, the terminal ends  104  include through holes  106  sized and shaped to receive bone screws  108  or other affixation structure. In this way, the implant  100  can be attached directly to tibia  112  of the knee joint  102 . Although the implant  100  is shown attached to the tibia  112 , it can also be affixed to the femur  110  as will be discussed further below. 
         [0063]    Although the present apparatus and method are described particularly for reducing pain of patellar chondromalacia or osteoarthritis due to damaged cartilage on the surfaces of the patella and the trochlear groove of the femur, embodiments of the disclosure can be used to relieve the loads on other joints in a similar manner. By changing the direction and position of tendons and muscles that exert forces on joints, the implants function as a tissue elevator to reduce compressive loads on joint surfaces. 
         [0064]    As shown in  FIG. 1 , the implant  100  is affixed to the tibia  112  such that a midsection  120  of the implant  100  is configured under the patellar tendon  130 . The terminal ends  104  of the implant  100  are shown directed away from the knee joint  102  but can alternatively be pointing toward the knee joint  102  or wrapping around the tibia  112 . 
         [0065]    The implant  100  is further contoured to define a low profile attachment structure. It is thus contemplated that a lower surface  140  of the implant  100  be curved to mimic the shape of the structure to which the implant engages, such as the tibia  112 , or femur  110 . An upper surface  142  is also contoured so as to fit nicely with the knee anatomy and may include a lubricious coating or material permitting relative motion between the implant and knee anatomy. The implant  100  may be provided in different sizes having different heights of the midsection  120  to allow a selection of different patellar tendon force reduction heights. 
         [0066]    Once an implant  100  of a selected height is inserted beneath the patellar tendon  130  the effective angle of action of the patellar tendon on the patella  90  is modified reducing the force with which the patellar tendon presses the patella against the femur. 
         [0067]    The upper surface  142  of the implant  100 , as shown in  FIG. 2 , further includes a recess  144  designed to receive the patellar tendon  130 . The recess  144  defines a trough through which the patella tendon  130  can be translated throughout a full range of articulation and valgus and varus motion or other rotation or movement of the knee joint. Thus, a portion of the patellar tendon  130  remains within the recess  144  throughout gait as well as when the knee joint  102  is in complete flexion or extension, and all angles therebetween, and when the knee joint is loaded and unloaded. Without the recess  144  or other structure for guiding the tendon over the implant  100 , the tendon can slide off of the implant during a portion of the motion of the joint. In addition to guiding the tendon  130  over the implant  100  in the ordinary natural path of the tendon, the implant may also be arranged to alter the path of the tendon and thereby correct improper tracking of the patella over the femur. For example, where the patella  90  is shifted medially and this shift is causing wear and associated pain in the joint, the implant  100  can shift the patellar tendon laterally to reorient the tracking of the patella while also reducing the load on the patella by changing the angle of action of the patellar tendon. In the case of redirecting the trajectory of the patellar tendon, the recess  144  in the implant  100  can be modified to have more pronounced edges to achieve this redirection. 
         [0068]      FIGS. 4A and 4B  illustrate a joint at extension with and without a tibial implant  100  and a femoral implant  600  secured to the tibia and femur with bone screws (not shown). The position of the tibial implant  100  beneath the patellar tendon  130  and the femoral implant  600  beneath the quadriceps muscle or quadriceps tendon  132  reduces the load on the patellar/femoral surfaces, thus reducing patellar/femoral pain. The reduction in contact between the patellar and femoral joint surfaces can be seen by comparison of  FIG. 4A  without implants to  FIG. 4B  with implants. The magnitude of reduction in contact is dependent on the implant height selected. A large implant height is shown in  FIG. 4B  by way of example to more clearly show the reduction in contact forces. The patella  90  need not be lifted entirely off the patella when the knee is at full extension to provide pain relief. 
         [0069]      FIGS. 5A and 5B  illustrate the reduction in load between the patella  90  and the femur  110  at about 30 degrees of flexion of the joint. As can be seen in  FIG. 5B , the distal portion of the patella  90  is lifted away from the femur  110 , significantly reducing load at this portion of the joint at partial flexion. 
         [0070]      FIGS. 6A and 6B  illustrate the reduction in load between the patella  90  and the femur  110  at about 75 degrees of flexion of the joint. As can be seen in  FIG. 6B , the proximal portion of the patella  90  is lifted away from the femur  110 , however the amount of load reduction my be tailored to the particular application by altering the configuration of the implants. 
         [0071]    The patellar implants  100 ,  600  can be configured to include one or more structures that only applies tension during gait, and then, during only portions of the gait cycle. Such structure can also include a load absorption component acting during such intervals. Through this approach, undesirable permanent remodeling of knee structure, and in particular unwanted lengthening of the patellar tendon, can be avoided. One way to achieve intermittent activation of the implant is to have a multi-compartment expandable implant which inflates and deflates based on joint action. These inflatable implants will be described in further detail below. 
         [0072]    Referring now to  FIGS. 7A-7C , the tibial implant  100  and femoral implant  600  can be used either alone or in combination. The implants of  FIGS. 7A-7C  have a C-shaped design that wraps around the bone shaft between 45 and 180 degrees of the circumference of the bone. The wrapping around of the C-shaped design allows several muscles and/or tendons to be redirected or repositioned by the implant. 
         [0073]      FIG. 8A  illustrates an I-shaped implant  610  configured to be attached to the femur  110 . At the position shown in  FIG. 8A  the implant  610  would reside partly beneath the patella (not shown) when the knee joint is at full extension. The I-shaped implant sits at the end of the femur  110  near the joint and elevates the quadriceps muscle and tendon. 
         [0074]      FIGS. 8B and 8C  illustrate two variations of an I-shaped implant for the tibia. The wider implant  160  extends beyond the bone contact region and the narrower implant  170  does not extend past this contact region. These implants are shown in further detail in  FIGS. 12A and 12B .  FIGS. 8D and 8E  illustrate J-shaped implants  180 ,  190  which have a single leg extending along the bone shaft for improved bone attachment. These different designs with different attachment mechanisms can provide the surgeon with options for attachment to bone with bone screw locations that avoid disruption to the ligaments, muscles and subchondral regions of the bone. 
         [0075]      FIGS. 9A-9D  illustrate different cross section profiles for the implants including those having top surfaces which are flat, saddle shaped, convex, or concave. These profiles can apply to both tibial implants  100  and femoral implants  600 . The implant of  FIG. 9A  has a concave lower surface  650  configured to correspond generally to the shape of the bone and a convex upper surface  652  configured to support the overlying tendon or muscles. Medial and lateral flanges  654  at the edges of the top surface help prevent the tendons or muscles from sliding off of the implant. A plurality of feet  656  on the lower surface  650  are configured to contact the bone and allow for the implant to accommodate different anatomical variations between patients. At least one foot  656  and preferably three feet extend from the implant on the bone-facing surface or bottom surface of the implant to make contact with the bone. The feet provide an offset which allows the implant to be seated on the bone surface despite slight variations in bone surface geometries between patients and despite slight variations in positioning of the implant. The feet  656  can be provided on any of the embodiments of the implants described herein and will tightly contact the bone or the periosteum when the bone screws are tightened to press the implant against the bone. 
         [0076]      FIG. 9B  has a concave lower surface  660  and a substantially flat upper surface  662  with lateral flanges  664 . Each of the implants has two or more holes for receiving bone screws.  FIGS. 9C and 9D  have various saddle shaped lower and upper surfaces with bone screws inserted from the proximal or distal side of the implant ( FIG. 9C ) and from the medial and lateral sides of the implant ( FIG. 9D ). The saddle top provides a stabilizing effect to keep the tendons or muscles from sliding off of the top of the implant. 
         [0077]    The flat top cross section of the implant  100   b  of  FIG. 10B  produces a one directional displacement of a tendon or muscle providing primarily unloading of the patella/femoral joint. The implant may also have an medial/lateral inclination as shown in the implant  100   a  of  FIG. 10A  to both reduce the load on the joint and also to shift the load on the joint medially or laterally. The implant  100   c  of  FIG. 10C  has a partly flat and partly angled surface which may both shift the load and reduce the load. 
         [0078]      FIGS. 11A-11C  show a series of implants of differing heights h. Implants having heights from 2 mm to 60 mm may be provided to allow the surgeon to select the implant that unloads the joint to the desired degree.  FIG. 11C  illustrates an offset height f provided by the feet  656 . The height f of the feet is about 2-5 mm, preferably about 3 mm. 
         [0079]      FIG. 12A  further illustrates the tibial implant  160  which has an overhang or projection  162  which extends by a distance X beyond a line formed at the bone contacting surfaces. This overhang  162  increases the effectiveness of the implant  160  at larger angles of flexion. The femoral implant  600  is also provided with an overhang  602 , however the overhang of the femoral implant does not extend beyond the joint contact surfaces. The implant  170  of  FIG. 12B  shows no overhang, however the implant is positioned close to or adjacent the joint contact surfaces. 
         [0080]    Referring to  FIGS. 13 and 14 , there is shown another embodiment of an implant  200 . As before, the implant can be generally U-shaped, C-shaped, I-shaped or J-shaped and includes terminal ends  204  configured to be affixed to body anatomy. Again, through holes are provided to receive affixation structure such as bone screws  108  so that the implant can be attached directly to knee anatomy. A lower surface  240  of the implant  200  be curved to mimic the shape of the structure to which the implant  200  engages, such as the tibia  112  or femur  110 . An upper surface  242  of the implant  200  is intended to be lubricous to permit relative movement with a patellar tendon  130 . Moreover, the implant  200  can be configured with its terminal ends  204  directed toward or away from the knee joint  102  and can include a midsection with a recess  244  shaped to receive the patellar tendon  130  through a full range of motion of the knee. 
         [0081]    This embodiment of the implant further includes a fluid, gas or gel filled chamber or bladder  250  which is accessible by an injection port  252 . The chamber  250  can form an integral structure with remaining portions of the implant  200  and portions of the implant  200  can embody fiber woven reinforced fixation material to form a single bodied structure. The injection port  252  is employed to both place substances within the chamber  200  and to be accessible to alter the volume or composition of the substance before and after implantation. The injection port  252  can also be used to remove all or most fluid when implanting or removing the implant  200  or to alter the softness or rigidity of the implant. The structure defining the chamber  250  can have an elasticity greater than that chosen for the remaining portions of the implant  200 , such as for example the terminal ends  204  which are designed to have a rigidity or robustness suited for permanent attachment to knee anatomy. The materials are of course chosen to be biocompatible in any event. 
         [0082]    The substance chosen to fill the chamber  250  is selected to cooperate with the material chosen for walls defining the chamber  250  so that desired load redirection can be effectuated. It is further contemplated to take advantage of fluid responses of the substances chosen for placement within the chamber  250 . For example, a viscous fluid or gel such as silicone hydrogel flows smoothly under low strain rates, but resists flow under high strain rates. Therefore, the fluid or gas chosen is intended to have a viscosity and the chamber walls are designed to have a flexibility to redirect load to alleviate pain. Such load redirection can be reserved to occur primarily gait, and for that matter, during only portions of gait with greater flexion angles. During joint extension, or otherwise when there is less pain due to forces associated with the patella this manipulation is reduced so that undesirable remodeling is avoided. 
         [0083]    Thus, as the knee joint  102  articulates during gait, the patellar tendon  130  is guided through the implant recess  244 . The load redirecting chamber  250  is sized and shaped to span the recess  244  so that during certain portions of gait having medium to high flexion angles, a height of the chamber  250  is at a maximum to provide maximum load redirection and reduced load applied directly between the patella  90  and femur  110 . For example, forces between the patella  90  and the femur  110  can be reduced and angles of action of the patellar tendon  130  can be modified to thereby minimize pain. 
         [0084]    In yet another approach ( FIGS. 15 and 16 ), the implant  300  can further include multiple chambers  350 ,  352  that are in fluid communication and which are versatile in accommodating tension and contact forces. As before, a lower surface  340  of the implant  300  be curved to mimic the shape of the structure to which the implant  300  engages, such as the tibia  112  or femur  110 . An upper surface  342  of the implant  300  is intended to be lubricous to permit relative movement with a patellar tendon  130 . Moreover, the implant  300  can be configured with its terminal ends  304  directed toward or away from the knee joint  102  and can include a midsection with a recess  344  shaped to receive the patellar tendon  130  through a full range of motion of the knee. 
         [0085]    The generally U-shaped device can be extended to provide a platform about each of the chambers  350 ,  352 . Here, again, the chambers  350 ,  352  are designed to receive gases or fluids which embody desirable viscosity characteristics. Additionally, the first chamber  350  is intended to be arranged to be in apposition with the patella tendon  130  and the second chamber  352  is to be positioned remote from the tendon  130  in an area where the chamber will be free to fill and empty in a relatively unobstructed manner. Also, as before, the walls defining the chambers  350 ,  352  are formed from materials having an elasticity designed to achieve desired force reorientation throughout the full range of motion of the knee joint. An injection port  354  is additionally included to provide access to the second chamber  352  so that the volume or composition of the substance in the chamber can be altered. 
         [0086]    A neck  356  joining the first  350  and second  352  chambers provides the fluid communication between the structures. A valve (not shown) can be configured in this area or the neck  356  can define a small opening. In either approach, the neck  356  can be configured to play a role in the movement of fluid from one chamber to the next. For example, when a leg of an individual is in extension, there is no force or little force on the first chamber  350 . The elasticity of the second chamber  352  is chosen to thus cause fluid to flow into the first chamber  350 . During gait, the sizing of the neck  356  is such that its flow access is limited so that there is insufficient time for fluid to pass from the first chamber  350  to the second chamber  352 . Rather, the fluid remains but flows within the first chamber  350  to thereby provide force reorientation. When seated or otherwise placing the knee joint  102  in other resting or non-gait positions, with the joint in flexion, the force of the patellar tendon  130  presses fluid out of the first chamber  350  into the second chamber  352 . As such, the first chamber  350  is reduced in size during this juncture, and the patellar tendon  130  is not subjected to the increased tension caused by the implant  300 . By not engaging in this manipulation, the patellar tendon  130  can be unloaded and remodeling thereof is avoided. 
         [0087]    In another embodiment, the second chamber  352  can be positioned within an anatomical structure, such as a muscle, and the fluid will be forced into the first chamber  350  by activation of the muscle. Therefore, the implant  300  can be activated by muscle activation, such as during running or walking, and can remain relatively passive at other times. 
         [0088]      FIGS. 17-20  illustrate a further embodiment of an implant  700  having a roller  710 . The implant  700  is designed to further reduce the friction between the implant and the tissue sliding over it. The roller  710  makes contact with the tendons, muscles and other tissues to reduce potential tissue irritation including tendonitis, inflammation, tendon tears and rupture. The roller  710  is supported in the implant  700  within blind bores  712  by bearing rollers  714 . Bearing rollers  714  are protected by a seal  716  in the form of O-rings, quad rings, lip seals or the like. 
         [0089]    In a related approach, as shown in  FIGS. 21-23 , an implant  400  designed to accomplish force reorientation can be affixed directly to the patellar tendon  130 . This implant  400  can further include one or more of the features described above including one or more fluid filled chambers. Further, it is again contemplated that the device be formed from biocompatible materials. This particular implant  400  further embodies a porous or mesh tendon contacting surface  402  and a lubricious bearing surface  404  for sliding contact with bone. The porous mesh surface  402  supports ligament ingrowth and aids in attachment to the patellar tendon  130 . The lubricious bearing surface  404  slides along knee anatomy during articulation. Through holes  406  are further provided and sized and shaped to receive fastening structures  410  for assuring a strong affixation to the patellar tendon  130 . In this way, relative movement between the implant  400  and ligament is eliminated and the implant  400  is thus always correctly positioned to provide desired force reorientation and pain relief. Other methods for attachment of the implant  400  to the patellar tendon  130  or other tendons or muscles may also be used including known tissue ingrowth surfaces on the implant, sutures, mechanical clamping or combinations of attachment mechanisms. There is no risk of the patellar tendon remodeling around the implant  400  because the implant is connected directly to the tendon. 
         [0090]    With reference to  FIG. 24 , there is shown in yet another embodiment of an implant  500 . This implant  500  can include one or more of the above described features, such as one or more chambers, and further embodies a generally inverted J-shape. A vertically extending portion  502  of the implant  500  is provided with through holes sized and shaped to receive fastening structure such as bone screws  108 . A laterally extending portion  508  includes a recess  510  for receiving a patellar tendon  130 . Although the implant  500  is shown attached to the tibia  112 , it can also be affixed to the femur  110  as well. This approach illustrates that an asymmetric implant can be employed to accomplish desired treatment of the patella  90 . A further deviation would be to eliminate the vertically extending portion  502  and to include affixation structure within the recess  510 . The implant  500  also has a trough or recess as in the implant shown in  FIG. 2  to guide in tracking the patellar tendon over the implant in a desired trajectory. 
         [0091]      FIG. 25  shows a hook shaped implant  500   a  which functions to both elevate the tendon  130  and to alter the tracking of the patella  90 . A hook  520  can move the patellar tendon and consequently the patella itself laterally, such as toward the lateral side of the knee when the patella pain is caused by improperly tracking to far to the medial side. The hook  520  is sized to receive at least a portion the tendon underneath the hooked portion of the implant. 
         [0092]      FIG. 26  illustrates a bridge shaped implant  800  which lifts the patellar tendon  130  in a manner similar to the lift implants shown herein, but lifts from the superior surface of the patellar tendon rather than from the inferior surface. The bridge can be attached to the patellar tendon  130  by sutures, mechanically clamped, tissue ingrowth or a combination thereof. 
         [0093]    The various embodiments of the implants describe herein may be made from a wide range of materials. According to one embodiment, the implants are made from metals, metal alloys, or ceramics such as, but not limited to, Titanium, stainless steel, Cobalt Chrome or combinations thereof. Alternatively, the implants are made from thermo-plastic materials such as, but not limited to, high performance polyketones including polyetheretherketone (PEEK), ultra-high molecular weight polyethylene (UHMWPE), PyroCarbon or a combination of thermo-plastic and other materials. Various embodiments of the implants are relatively rigid structures. 
         [0094]    Conventional approaches to inserting the above-described implants within knee anatomy are contemplated. Arthroscopic approaches can be employed along with fluoroscopy or other imaging techniques to properly position the treatment devices. Prior to implantation, the anatomy of the patient&#39;s knee is accessed to determine a best course of treatment, and to identify a configuration of implant which best suits the patient&#39;s specific condition. The knee is rotated and turned through its full range of motion to identify proper implantation sites and to access the best manner for redistributing tensions and contact forces, with the objective of reducing pain. Further, the implant is configured in its most compressed configuration for implantation and then reconfigured to function in a treatment capacity. Subsequent to implantation, the implant can be reconfigured to present an altered profile to achieve optimum results. 
         [0095]    The foregoing therefore provides an implant embodying a compliant bolster and lengthening affect to increase a moment arm of the bolstered patellar tendon for the purpose of relieving pain or other symptoms involving the patella. The size or stiffness of the implant can be altered to achieve the desired bolstering or manipulation of tension and contact forces. 
         [0096]    Thus, it will be apparent from the foregoing that, while particular forms of the apparatus and method have been illustrated and described, various modifications can be made without parting from the spirit and scope of the disclosure. In particular, one or more features of one specific approach can be incorporated into another approach. Additionally, the present disclosure can be made to be applicable to other medical conditions.