Piriformis is a short muscle deep in the buttocks which arises from the sacral bone and is attached to the top of the femur at the hip. Piriformis syndrome happens when the muscle doesn’t recover from a trauma if not healed. Further damage can occur which can lead too much tightening to the muscle. Stretching the tight muscle will cause more pain when it is moved. Thigh rotation movement like switching directions whilst walking or running will aggravate your condition. There is no long-term damage and usually heals in a number of days to weeks, as long as you consult a sports physiotherapist for assistance.