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Semimembranosus

The semimembranosus (also semimembranosus muscle, latin: musculus semimembranosus) is a flat, long muscle situated in the posterior region of the thigh.

The semimembranosus is so called because of its membranous tendon of origin.

Origin

The semimembranosus originates from the ischial tuberosity.

Insertion

The semimembranosus muscle inserts onto the medial condyle of the tibia.

Action

The main functions of the semimembranosus are extension of the thigh at the hip joint, and flexion and internal rotation of the knee.

Innervation

The semimembranosus is innervated by the tibial nerve, a branch of the sciatic nerve, which arises from the sacral plexus.