The extent of pain in sciatica is mainly limited to the area of the sciatic nerve distribution, mainly the posterior thigh, the posterior lateral calf and the foot. When the sciatic nerve is compressed, pain occurs in these areas of sciatic nerve innervation. Patients with severe pain may also have a characteristic posture, such as lumbar flexion, knee flexion, and foot-first landing, and some patients with long-standing disease may also have memory loss, partial weakness or paralysis of the muscles innervated by the sciatic nerve, and possibly decreased or absent Achilles tendon reflexes. In the area innervated by the sciatic nerve, there may be a loss of sensation, including a loss of vibration in the outer ankle, and there may be minimal sensory disturbances.