What is piriformis syndrome?

Piriformis syndrome is a neuromuscular condition that occurs when the piriformis muscle in the buttocks pinches the sciatic nerve. The piriformis muscle is a large muscle on each side of the buttocks. The sciatic nerve is a nerve which starts at the spinal cord in the low back, extends through the piriformis muscle in the buttock, and branches down the back of the leg, all the way to the foot.