What causes piriformis syndrome?

Piriformis syndrome can be caused by an injury to the pelvis or buttock after a fall or a slip. It can happen in people who are very active but who use their muscles asymmetrically. It also can happen in people with a condition affecting their spine, such as scoliosis, when the stress on the pelvis is asymmetric and causes unusual turns and twists that put the piriformis muscle into spasm. The piriformis muscle is a small muscle located deep within each buttock. In some cases, if the piriformis muscle is inflamed or in spasm, it becomes hard and tight like a ball. It presses on the sciatic nerve and eventually can irritate and damage the nerve. Sometimes in the body, a branch of a nerve or an entire nerve will pass through a muscle. It doesn’t take much muscle inflammation to really irritate a nerve that’s sitting right in the middle of a muscle.