According to the Cleveland Clinic, piriformis syndrome causes pain or numbness in a person’s butt, hip or leg. The pain typically occurs when the body’s piriformis muscle presses on the sciatic nerve which results in inflammation.

Piriformis syndrome is a rare neuromuscular condition that happens when the piriformis muscle in the butt presses on the sciatic nerve, according to the Genetic and Rare Diseases Information Center (GARD).