Piriformis Syndrome

The piriformis syndrome is a controversial condition in which the piriformis muscle irritates the sciatic nerve  It causes pain in the buttocks which is referred pain along the course of the sciatic nerve. It is one cause of "sciatica." Patients generally complain of pain deep in the buttocks, which is made worse by sitting, climbing stairs, or performing squats. The piriformis muscle assists in abducting (pulling outward) and laterally rotating (turning out) the thigh. Stretching the muscles can duplicates the pain.

Anatomically, the piriformis muscle lies deep to the gluteal muscles. It originates from the sacral spine and attaches to the greater trochanter of the femur, which is the big, bony "bump" on the outside top of the thigh. In approximately 15% of the population, the sciatic nerve travels through the muscle. It is thought that acute or chronic injury causes swelling of the muscle and irritates the sciatic nerve, resulting in sciatica.

The piriformis syndrome is diagnosed primarily on the basis of symptoms and on the physical exam. There are no tests that are 100% accurate,  but X-rays, MRI, and nerve conduction tests may exclude other diseases and a local dye injection can show if the nerve is pinched by the pyriformis muscle.

Treatment is undertaken in a stepwise approach. Initially, progressive piriformis stretching is employed.  If this fails, then injections of a corticosteroid into the piriformis muscle may be tried. Surgery used to be popular for this condition but research shows that it rarely helps.

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Last modified: 07/27/08