Viewer Question:When I drive my auto for more than a half hour I get a pain on the underside of my right leg from below the knee to right below the buttock. Putting the auto into cruise control and positioning my right leg straight up and down sometimes stops the pain. What is the sciatic nerve, which my wife says is the problem?
Doctor's Response:The sciatic nerves are large nerves that begin from fibers that exit the spinal column on either side of the lower spine (fourth and fifth lumbar and first and second sacral levels). The sciatic nerves exit the pelvic bone through an opening (greater sciatic foramen) to emerge in the buttock (gluteal region). It travels down the thigh from below the buttock. At this point the nerve is nearest the surface. The nerve travels down the thigh past the leg sending fibers to the sole of the foot.
The sciatic nerve supplies electrical impulses that signal the muscles of the hamstring and muscles below the knee. The sciatic nerve also carries the impulses of sensation including pain, temperature, vibration, and position from the back of the thigh and leg, and bottom of the foot.
Because your pains are felt after you are sitting for a period in your auto, it is very likely that they are a result of direct pressure upon the sciatic nerve at its most superficial point just below the buttock. (Always listen to your wife!) This problem is particularly common when sitting for prolonged periods in bucket seats.
Irritation of the sciatic nerve from anything pushing direct pressure on it at any point can cause painful symptoms along its distribution. This includes abnormalities of the bone, muscle, spinal discs, spinal cord, and tumors of the pelvis.
Last Editorial Review: 9/25/2005