Piriformis syndrome is an uncommon neuromuscular disorder that is caused when the piriformis muscle compresses the sciatic nerve. The piriformis muscle is a flat, band-like muscle located in the buttocks near the top of the hip joint. This muscle is important in lower body movement because it stabilizes the hip joint and lifts and rotates the thigh away from the body. This enables us to walk, shift our weight from one foot to another, and maintain balance. It is also used in sports that involve lifting and rotating the thighs -- in short, in almost every motion of the hips and legs.
Piriformis syndrome usually starts with pain, tingling, or numbness in the buttocks. Pain can be severe and extend down the length of the sciatic nerve (called sciatica). The pain is due to the piriformis muscle compressing the sciatic nerve, such as while sitting on a car seat or running. Pain may also be triggered while climbing stairs, applying firm pressure directly over the piriformis muscle, or sitting for long periods of time.