Semimembranosus

The semimembranosus (Latin: musculus semimembranosus) is a flat and long muscle situated in the posterior compartment of the thigh. It is the most medially located muscle in the posterior compartment, and next to it lies the semitendinosus muscle. The semimembranosus stretches between the hip and knee joints. The semimembranosus, semitendinosus and biceps femoris are all known as hamstring muscles.

Origin

The semimembranosus muscle originates from the ischial tuberosity.

Insertion

The semimembranosus inserts on the medial condyle of the tibia.

Action

The semimembranosus muscle provides the extension of the thigh at the hip joint and flexion and internal rotation of the leg at the knee joint.

Innervation

The semimembranosus is innervated by the tibial nerve - a branch of the sciatic nerve (L5 - S2) that arises from the sacral plexus.

Blood supply

The semimembranosus muscle receives arterial blood supply from the branches of the deep femoral, inferior gluteal and popliteal arteries. The deep femoral artery arises from the femoral artery, the inferior gluteal artery is a branch of the internal iliac artery, and the popliteal artery is a continuation of the femoral artery.