Biceps femoris muscle

The biceps femoris is one of the three hamstring muscles located in the posterior compartment of the thigh. It has two heads—a long head and a short head—which converge to form a common tendon inserting onto the head of the fibula.

Origin

1. Long head

• Arises from the inferomedial part of the ischial tuberosity by a common (conjoined) tendon with the semitendinosus.

2. Short head

• Arises from the lateral lip of the linea aspera and the upper part of the lateral supracondylar line of the femur, as well as from the lateral intermuscular septum.

Insertion

• The two heads unite in the lower third of the thigh to form a strong tendon, which inserts mainly into the head of the fibula. Some fibres may also insert into the lateral condyle of tibia and deep fascia of leg.

Innervation

• Long head: Tibial division of the sciatic nerve (L5–S2)

• Short head: Common fibular (peroneal) division of the sciatic nerve (L5–S2)

Action

Both heads cause flexion at the knee joint, along with lateral rotation of the joint (when the knee is flexed). In addition, the long head also contributes to extension at the hip joint.