The biceps femoris is a double-headed muscle located on the back of thigh. It consists of two parts: the long head, attached to the ischium (the lower and back part of the hip bone), and the short head, which is attached to the femur bone.

The long head is a part of the hamstring muscle group that occupies the posterior section of the thigh. The hamstring muscles may be considered extensors of the thigh. The biceps femoris muscle is important for knee flexion, internal and external rotation, and hip extension.

Pain in the biceps femoris can be caused by several reasons. The most common condition is a strained muscle caused by improper lifting or too much exercise. Overuse of the biceps femoris can result in torn muscles and ligaments.