injuries and poisoning
Piriformis Syndrome
Introduction
Piriformis syndrome is compression of the sciatic nerve by the piriformis muscle (a flat muscle of the buttocks located near the hip), causing pain in the buttocks and occasionally sciatica. (See also Overview of Sports Injuries .) The piriformis muscle extends from the pelvic surface of the large triangular bone at the base of the spine (sacrum, or tailbone) to the bony bump (trochanter) at the upper end of the thighbone (femur). During running or sitting, this muscle can compress the sciatic nerve at the site where it emerges from under the piriformis to pass over the hip rotator muscles. Piriformis syndrome is uncommon. 