Piriformis syndrome is a condition in which the muscle called piriformis — the small one in the buttock region — spasms and causes pain in the buttock area, lower back, and even the whole leg at times. This muscle also often irritates the sciatic nerve located nearby and causes numbness and tingling, and sometimes severe pain along the back of the leg and into the foot, similar to what happens with sciatic pain, another conditions which piriformis syndrome is often confused with.
Piriformis is a small muscle located behind the gluteus maximus. It starts at the lower spine and connects to the left and right femur, better known as the thigh bones. This muscle helps in the hip rotation and turning the leg outwards.
The pain in the buttocks is most often caused by macrotrauma in the buttock area, muscle spasms, and inflammation of soft tissue. Microtrauma may occur from overuse of the muscle, most commonly in those who walk long distances, and runners.