Semitendinosus
Musculus semitendinosus
Also known as: medial hamstring
A superficial medial hamstring with a fusiform belly and a long cord-like tendon (hence "half-tendon"). It inserts in the pes anserinus.
Overview
Semitendinosus arises from the ischial tuberosity in a common tendon with the long head of biceps femoris. Its belly, often divided by a tendinous intersection, lies on semimembranosus. About halfway down the thigh it becomes a long, round tendon that runs along the medial side of the popliteal fossa. It passes behind the medial femoral condyle and inserts on the upper medial tibia as the most posterior member of the pes anserinus, behind gracilis and sartorius.
It extends the hip, flexes the knee and medially rotates the flexed leg. Its tendon, often taken together with gracilis, is the most popular autograft for anterior cruciate ligament reconstruction. It can regenerate a tendon-like structure after harvest.
Anatomy
- Origin
Ischial tuberosity (inferomedial impression, common tendon with the long head of biceps femoris).
- Insertion
Superior part of the medial surface of the tibia (pes anserinus).
- Action
Extension of the thigh; flexion of the leg; medial rotation of the flexed knee.
- Innervation
Tibial division of the sciatic nerve.
- Nerve roots
L5–S2
- Arterial supply
Perforating branches of the profunda femoris; inferior gluteal artery; medial genicular arteries.
- Relations
Lies superficial to semimembranosus. Its tendon forms part of the superomedial border of the popliteal fossa.
Function
- Extends the hip
- Flexes the knee and medially rotates the flexed leg
Clinical significance
ACL graft
The semitendinosus (± gracilis) tendon is harvested through a small incision over the pes anserinus. The saphenous nerve's infrapatellar branch is at risk.
Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.