The biomechanics of the patellofemoral joint.

Physical therapy for patella malalignment differs from therapy for other knee conditions. In fact, accepted forms of knee therapy can be counterproductive when one is dealing with patella malalignment. This article reviews some of the biomechanical foundations of patella-specific therapy and addresses common controversies. We emphasize the concept of articular cartilage stress over that of joint reaction force. The rationale for strengthening the vastus medialis obliquus and for avoiding certain forms of open chain strengthening are discussed, and we outline some of the exciting work being done in our laboratory concerning patellofemoral tracking, contact area, and cartilage properties.