The posterior compartment of the thigh consists of the following muscles:

Semitendinosus

The semitendinosus muscle is a long, thin muscle located in the posterior region of the thigh and superficially to the semimembranosus. The semitendinosus is so called because of the long length of its tendon of insertion, extending from the middle of the thigh.

Origin: ischial tuberosity.

Insertion: the tendon of the semitendinosus muscle together with the tendon of the sartorius muscle and tendon of the gracilis muscle form a common plate - pes anserinus - that inserts into the proximal end of the tibia below the medial condyle.

Action: extension of the thigh, flexion and internal rotation of the leg.

Innervation: tibial nerve of the sciatic nerve (L5 - S2).

Blood supply: branches of the femoral artery, internal iliac artery and popliteal artery.

Semimembranosus

The semimembranosus muscle is a flat, long muscle situated in the posterior region of the thigh. The semimembranosus is so called from its membranous tendon of origin.

Origin: ischial tuberosity.

Insertion: medial condyle of the tibia.

Action: extension of the thigh, flexion and internal rotation of the leg.

Innervation: tibial nerve of the sciatic nerve (L5 - S2).

Blood supply: deep femoral artery, inferior gluteal artery and popliteal artery.

Biceps femoris

The biceps femoris muscle is a two-headed muscle located in the posterior region of the thigh.

Origin: the long head of the biceps femoris muscle originates from the ischial tuberosity (on the superior ramus of the ischium), while the short head of the biceps femoris muscle arises from the lateral lip of the linea aspera and the lateral supracondylar line of the femur (on the posterior surface of the femoral shaft).

Insertion: both heads of the biceps femoris insert into the lateral aspect of the head of the fibula.

Action: entire muscle - flexion and external rotation of the leg; the fibers of the long head of the biceps femoris also aid in extension and external rotation of the thigh.

Innervation: long head - tibial nerve (L5 - S2), short head - common peroneal (fibular) nerve (L5 - S2).

Blood supply: perforating branches of the deep femoral artery, medial circumflex femoral artery, inferior gluteal artery, branches of the popliteal artery.

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Posterior compartment of thigh muscles