Semimembranosus

The semimembranosus is a muscle within the posterior compartment of the thigh. It is located deep to the semitendinosus muscle within the medial aspect of the posterior thigh.

• Attachments: Originates from the ischial tuberosity (more superiorly than the origin of the semitendinosus and biceps femoris). Attaches to the medial tibial condyle.
• Actions: Flexion of the leg at the knee joint. Extension of thigh at the hip. Medially rotates the thigh at the hip joint and the leg at the knee joint.
• Innervation: Tibial part of the sciatic nerve.
• Blood Supply: Profunda femoris artery.

By TeachMeSeries Ltd (2025)

Fig 1
The muscles of the posterior thigh.

By TeachMeSeries Ltd (2025)

Fig 2
Cross section of the thigh, showing the position of the major muscle groups.