The term "sciatica" commonly refers to a pain which extends from the sacroiliac region into the posterior or posterolateral part of the thigh and calf or lateral portion of the leg. The pain may continue as far as the heel or even into the lateral border of the foot. This pain is almost always caused by the presence of a pathological process affecting the sciatic nerve, the lumbosacral plexus or the fourth lumbar, fifth lumbar or first sacral nerve roots. Pain that extends only from the lumbosacral junction to the inferior margin of the gluteal fold or to the midportion of the posterior part of the thigh should not be classed as sciatica and may be due to pathological processes which do not affect the sciatic nerve or any of the fibers which form it. The diagnosis of the cause of sciatica depends on evaluation of a composite examination that