The sciatic nerve is composed of both sensory and motor fibers, wrapped in a common connective tissue sheath. It originates from the sacral plexus and exits the pelvis through the infrapiriform foramen. It runs down beyond the gluteus maximus muscle, along the posterior aspects of the internal obturator muscle. Right above the knee joint, the sciatic nerve bifurcates into the common peroneal and tibial nerves.
The motor fibers of the sciatic nerve suppy four muscles of the lateral rotator group: superior gemellus, obturator internus, obturator externus, inferior gemellus. (the lateral rotator group are six small muscles of the hip). It also innervates the posterior compartment of thigh. The sensory fibers of this nerve suppy the skin on the gluteal region, the posterior aspects of the thigh, and the lower leg.