Piriformis syndrome, hip muscle spasm due to pressure on the sciatic nerve
The piriformis muscle, a flat, band-like structure located near the top of the hip joint in the buttocks, is involved in significant lower body movement, and used extensively in sports such as running and biking. It overlies the sciatic nerve, the long main nerve that extends down the back of the leg. The sciatic nerve branches out into smaller nerve endings in the feet. The sciatic nerve innervates the hamstring muscles and all of the muscles below the knee. It also provides feeling to the feet. Nerve compression