Semitendinosus

The semitendinosus (Latin: musculus semitendinosus) is a long fusiform-shaped muscle located in the posterior compartment of the thigh next to the semimembranosus and biceps femoris muscles. It extends between the femur and tibia. The semitendinosus, semimembranosus and biceps femoris muscles all are known as hamstring muscles. The semitendinosus is so-called because of the prominent length of its insertion tendon.

Origin

The semitendinosus muscle originates from the ischial tuberosity of the ischium.

Insertion

The semitendinosus inserts on the proximal end of the tibia below the medial condyle via the pes anserinus. The distal end of the semitendinosus tendon blends with tendons of the sartorius and gracilis muscles forming a common tendon called the pes anserinus.

Action

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

Innervation

The semitendinosus is innervated by the tibial nerve - a branch of the sciatic nerve (L5 - S2).

Blood supply

The semitendinosus muscle receives arterial blood supply from the branches of the femoral (deep femoral artery, perforating branches), internal iliac (inferior gluteal artery) and popliteal arteries.