1. One of the tendons bounding the popliteal space on either side; the medial hamstring comprises the tendons of the semimembranosus and semitendinosus, gracilis, and sartorius muscles; the lateral hamstring is the tendon of the biceps femoris muscle. Hamstring muscles (a) have origin from the ischial tuberosity, (b) act across (at) both the hip and knee joints (producing extension and flexion, respectively), and (c) are innervated by the tibial portion of the sciatic nerve. The medial hamstring contributes to medial rotation of the leg at the flexed knee joint, while the lateral hamstring contributes to lateral rotation.
2. In domestic animals, the combined tendons of the superficial digital flexor, triceps surae, biceps femoris, and semitendinosus muscles which are referred to as the common calcanean tendon (tendo calcaneus communis); it is attached to the tuber calcis of the hock.