Medial patella anatomy and stabilization

During extension of the knee, the femoral muscles (quadriceps femoris, vastus medialis, and vastus lateralis) apply an oblique, laterally displacing force to the patella (black arrow, top figure). The medial patellofemoral ligament and the vastus medialis obliquus (lower figure) provide medial stabilization of the patella against potential patellar subluxation or dislocation.