Piriformis syndrome is sciatica-like pain due to impingement of the sciatic nerve as it courses through the piriformis muscle. It can be located only within the piriformis muscle or radiate different degrees all the way to the foot. The incidence is thought to be 6% to 8% of all low back pain cases and is most often noted in the 30 to 40 year old age group. The female-to-male ratio is thought to be 3 to 6:1. The piriformis muscle is the largest of the short external rotators of the hip. Other external rotators of the hip include the superior and inferior gemellus, quadratus femoris and obturator internus muscles which all may be involved as well. The piriformis muscle originates from the second to fourth sacral vertebrae, exiting the pelvis through the sciatic notch and inserting on the upper portion of the greater trochanter with variations in the course of the sciatic nerve through the piriformis muscle. The exact mechanism of this type of sciatica remains unknown, although theories include nerve entrapment due to adhesions from an initial injury such as a fall; compression due to myofascial pain; or compression of the nerve by the muscle or tendon with hip internal rotation.
If your piriformis muscle is compromised, even simple normal activities can cause the piriformis muscle to spasm and become painful. Activities that can worsen the pain include arising from a chair, walking up stairs or standing for a long period of time. Any activity that increases hip external rotation can increase the pain. Also blunt trauma to the gluteal region, pregnancy and prolonged sitting on hard surfaces can also be factors in piriformis syndrome.
Piriformis syndrome is considered a diagnosis of exclusion with no consensus on clinical findings. Most importantly it is critical to rule out a pinched nerve in the lower back, because it has “sciatica-like” features such as buttock and lower leg pain. Also a progressive limp may overload adjacent structures worsening the pain.
Other diseases that can mimic piriformis syndrome include:
• Herniated nucleus pulposus
• Hip joint pathology
• Pelvic tumors
• Sacroiliac joint pathology
• Spinal stenosis
The symptoms of piriformis syndrome can respond quite well to non-surgical treatments. In some cases, pain can be temporarily or permanently relieved.
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Papadopoulos EC, Khan SN. Piriformis syndrome and low back pain: a new classification and review of the literature. Orthop Clin North Am. 2004 Jan;35(1):65-7.