Piriformis syndrome is a disorder in which the piriformis muscle in the buttocks irritates the sciatic nerve i.e. it occurs when the sciatic nerve gets compressed by the Piriformis muscle.

Piriformis syndrome is a disorder of a narrow muscle located in the buttocks. Symptoms include pain, tingling, or numbness in the buttocks and down the leg, which may worsen after sitting for a long time, climbing stairs, walking, or running.