Hamstring muscles are in the back of the thigh, starting at the hip and inserting to the knee. The three hamstring muscles are:
- Biceps femoris, closest to the outside of your body. The function of this hamstring is to flex your knee, extend the thigh at your hip and rotate your lower leg from side-to-side when your knee is bent.
- Semimembranosus, closest to the middle of your body. This hamstring flexes your knee joint, extends your thigh at your hip and offers medial rotation for your hip and lower leg.
- Semitendinosus, between the semimembranosus and the biceps femoris. The function of this hamstring matches that of the semimembranosus.