Summary Biceps femoris long head Origin Superior medial quadrant of the posterior portion of the ischial tuberosity Insertion Primarily on fibular head; also on lateral collateral ligament and lateral tibial condyle Action Flexes the knee, and also rotates the tibia laterally; long head also extends the hip joint Innervation Tibial nerve (L5, S1, S2) Arterial supply Perforating branches of profunda femoris artery, inferior gluteal artery, and the superior muscular branches of popliteal artery