A chronic PELVIC PAIN characterized by pain deep in the buttock that may radiate to posterior aspects of the leg. It is caused by the piriformis muscle compressing or irritating the SCIATIC NERVE due to trauma, hypertrophy, inflammation or anatomic variations.

Either of two fleshy protuberances at the lower posterior section of the trunk or HIP in humans and primate on which a person or animal sits, consisting of gluteal MUSCLES and fat.

An involuntary contraction of a muscle or group of muscles. Spasms may involve SKELETAL MUSCLE or SMOOTH MUSCLE.