Piriformis syndrome is caused by a tight contracted piriformis muscle putting pressure on the sciatic nerve causing symptoms of tingling, numbness, and altered sensation. This muscle is often tight in people who sit for long periods of time. A common cause of this muscle being contracted and tight are trigger points. These trigger points are contracted knots within the belly of the muscle. These knots cause the muscle to become shortened. Trigger points will also cause pain on their own. This is usually felt as a deep achy pain in the glute and hip area, as well as in the back of the leg.