The motor functions of the knee are primarily serviced by the sciatic nerves, which are branches of the lumbar nerves and are the largest and longest nerves in the body. They descend into the buttock and into the thighs, where they divide into the tibial and common peroneal nerves. The many branches of these nerves supply nerve impulses to and from the muscles and skin in the hip joints and thighs, the lower legs, feet and most of the skin below the knee.