The semitendinosus (also semitendinosus muscle, latin: musculus semitendinosus) is a long, thin muscle located in the posterior region of thigh superficially to the semimembranosus muscle.
The semitendinosus is so called because of the prominent length of its tendon of insertion that extends from the middle of the thigh down to the tibial tuberosity.
The semitendinosus originates from the ischial tuberosity.
The tendon of the semitendinosus inserts onto the tibial tuberosity.
The functions of the semitendinosus are extension of the thigh at the hip joint, and flexion and internal rotation of the knee.
The semitendinosus is innervated by the tibial nerve, a branch of the sciatic nerve, which arises from the sacral plexus.