The Great Sciatic Nerve is the largest in the body. It is derived from the lumbo-sacral plexus, and issues from the great sciatic opening as a broad white band; thence it takes a downward course between the sacro-sciatic ligament and the gluteus maximus. On reaching the thigh it is lodged between the biceps femoris and semitendinosus, having the semimembranosus and great adductor of the thigh supporting it within.

On nearing the leg it passes between the two heads of the gastrocnemius muscle, when it takes the name of the internal popliteal nerve. This is continued on as the posterior tibial, which dividing, forms the internal and external plantar nerves. In its course down the limb it supplies a slender branch to the obturator intern us, pyriformis, gemelli, and quadratus femoris.