The biceps femoris (also biceps femoris muscle, latin: musculus biceps femoris) is a two-headed muscle of the lower limb located in the posterior region of the thigh. The biceps femoris has two portions - the long head and the short head.
The long head of the biceps femoris originates from the back part of the ischial tuberosity on the superior ramus of the ischium, while the short head of the biceps femoris arises from the lateral lip of the linea aspera on the posterior surface of the shaft of the femur.
Both heads of the biceps femoris insert onto the head of the fibula.
The functions of the biceps femoris are flexion and external rotation of the knee. The fibers of the long head of the biceps femoris also aid in extension of the thigh.
The long head of the biceps femoris is innervated by the tibial nerve, but the short head is supplied by the common peroneal nerve. Both of these nerves are terminal branches of the sciatic nerve, which arises from the sacral plexus.