The piriformis muscle is a small muscle in the groin that runs from the sacrum to the outer hip bone. If the piriformis muscle becomes tight or cramps it can put pressure on the sciatic nerve which passes underneath the piriformis muscle. Typically this pain increases when the muscle contracts, when sitting for an extended time, or direct pressure on the muscle. Gluteal (or buttock) pain is common. Pirformis syndrome is also a common cause of sciatica.
Pain can also be caused by prolonged external rotation of the hip so that the piriformis muscle is shortened. If the sciatic nerve is compressed for an long time there may be aching in the leg and pain in the low back.
Shortening of the muscle and compression of the nerve is the most common cause of piriformis Syndrome, but overuse of the gluts and other muscles in the hip can also cause muscle spasms of the piriformis. Other factors in this syndrome include poor body mechanics and posture, gait problems.
Stretching and strengthening are the best treatments for piriformis syndrome. This muscle rarely gets stretched, so a simply stretching routine can often work wonders.
To stretch the right piriformis: lay on your back, bend your knees and cross your right leg over your left so your right ankle rests on your left knee in a figure four position. Bring your left leg towards your chest by bending at the hip. Reach through and grab your left thigh to help pull things towards your chest.
If stretching alone doesn't help check with a physician or physical therapist who can check your pelvic and foot mechanics.