Semitendinosus muscle

At a glance

English

Semitendinosus muscle

Latin (TA2)

Musculus semitendinosus

System

Muscle

Region

Lower limb

Side

Paired, left and right

About the semitendinosus muscle

Semitendinosus is one of the three hamstrings on the back of the thigh, lying medially and superficially, on top of semimembranosus. Its name refers to its striking tendon, which makes up almost the whole lower half of the muscle. In the thigh it sits between biceps femoris laterally and semimembranosus deeply and medially.

It arises from the lower inner facet on the ischial tuberosity by a tendon it shares with the long head of biceps femoris, and from a short aponeurosis linking the two muscles for several centimetres. Its fusiform belly, often crossed by a tendinous band, gives way, a little below mid-thigh, to a long, rounded tendon. This descends along the inner border of the popliteal fossa, curves round behind the medial tibial condyle and crosses the medial collateral ligament, separated from it by a bursa. It attaches to the upper medial surface of the tibial shaft, reaching nearly to the front edge of the bone.

At the insertion its tendon lies behind that of sartorius and below that of gracilis, and the three join to form the pes anserinus, named for its resemblance to a goose's foot. Like the other hamstrings it extends the hip and flexes the knee. When the knee is bent it rotates the tibia inwards, and with the hip straight it helps turn the thigh inwards. It also controls the pelvis when leaning forwards from the hips. Its nerve is the tibial division of the sciatic nerve, and its blood comes from the perforating branches of the deep femoral artery and the inferior gluteal artery.

The tendon is long, strong and easily harvested, so with gracilis it is one of the commonest grafts used to rebuild a torn anterior cruciate ligament. Hamstring strains often involve this muscle in sprinting, and the pes anserine bursa beneath the joined tendons may become painfully inflamed.

Attachments, action and supply

Origin

Inferomedial impression on the ischial tuberosity, by a tendon shared with the long head of biceps femoris.

Insertion

Upper medial surface of the tibia, behind sartorius and below gracilis, as part of the pes anserinus.

Action

Extends the hip and flexes the knee; medially rotates the flexed leg and assists medial rotation of the extended thigh.

Nerve supply

Tibial division of the sciatic nerve (L5, S1, S2).

Blood supply

Perforating branches of the deep femoral artery and the inferior gluteal artery, with medial genicular branches near the knee.