Ruptures of the extensor mechanism of the knee are debilitating injuries that typically require surgery and prolonged physical therapy. The severity of this injury is due in part to the central role that knee extension plays in the activities of daily living. Anatomically, the knee extensor mechanism is composed of four principal components: the quadriceps femoris muscles (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius), the quadriceps tendon, the patella, and the patellar tendon. The tendinous portions of the quadriceps muscles typically coalesce into the quadriceps tendon 3 cm proximal to the superior pole of the patella. From the patellar insertion, the anteriormost rectus femoris component of the quadriceps tendon continues over the anterior surface of the patella, joining the patellar tendon at the inferior patellar pole. The patellar tendon subsequently inserts into the tibial tubercle.