Posterior Group of Thigh Muscles

The posterior group of thigh muscles is sometimes referred to as the hamstring muscles. It is composed by three long powerful muscles, all of them arising from the ischial tuberosity of pelvis, stretching along the full length of femur. Their upper (proximal) portions are covered by the gluteus maximus. They are:

1- The semimembranosus muscle, which lies on the medial border of the posterior side of thigh. Origin: ischial tuberosity. Insertion: medial condyle of tibia and oblique posterior ligament of knee.

2- The semitendinosus muscle, which lies closer to the medial border, extending over the semimembranosus. Origin: ischial tuberosity. Insertion: tubercle of tibia.

3- The biceps femoris muscle, which extends vertically on the lateral border of posterior side of thigh. Long and flattish, it arises from the ischial tuberosity of pelvis ischium and get inserted into the proximal end of tibia.

Action/function

They extend the thigh at the hip-joint, flexing the leg at the knee, rotating medially and laterally.

Innervation

The posterior group of thigh muscles are innervated by the tibial (L4-L5-S1) and sciatic nerves (S1-S2).

Blood Supply

They receive oxygenated blood from branches of the medial circumflex femoral, perforating, and popliteal artery.

Below, the schematic picture of posterior aspect of right thigh, showing all three muscles of posterior group.