Leg muscles. Historical artwork of the muscles of the leg, revealed by removing the skin and surface tissue. The main muscles of the back of the thigh (upper leg) include the gluteus maximus and the biceps femoris. On the front of the thigh, the main muscle is the rectus femoris. The thin muscle between them is the sartorius muscle, the longest muscle in the human body. The calf muscles (on the back of the lower leg) are called the gastrocnemius muscles, while the tibialis anterior is the main muscle in the shin (the front of the lower leg). The strap-like foot ligaments and muscles are also shown.