Piriformis syndrome is a neuromuscular ailment in the event the piriformis muscle mass (a pear-shaped muscle within the buttocks) compresses the sciatic nerve (a nerve that extends from the lower backbone each of the way down to the foot). This ends in pain in the buttocks and hips. Illustrations on https://www.theorthopaedicandpainpractice.com/lower-back-and-buttock-pain/