In this condition, the patella repetitively subluxates and places strain on the medial restraints and excessive stress/tension on the patellofemoral joint. Patellar subluxation can be caused by osseous abnormalities, such as incorrect articulation of the femoral groove with the patella, trochlear dysplasia, or patella alta, which is a distance of greater than 20 mm between the tibial tubercle and the trochlear groove. It can also result from soft-tissue abnormalities, such as a torn medial patellofemoral ligament, or a weakened vastus medialis obliquus.[2] Symptoms are regulated by the amount of activity.