Piriformis syndrome is an uncommon neuromuscular disorder that is caused when the piriformis muscle compresses the sciatic nerve. The piriformis muscle is a flat, band-like muscle located in the buttocks near the top of the hip joint. This muscle is important in lower body movement because it stabilizes the hip joint and lifts and rotates the thigh away from the body. This enables us to walk, shift our weight from one foot to another, and maintain balance. It is also used in sports that involve lifting and rotating the thighs -- in short, in almost every motion of the hips and legs.
The sciatic nerve is a thick and long nerve in the body. It passes alongside or goes through the piriformis muscle, goes down the back of the leg, and eventually branches off into smaller nerves that end in the feet. Nerve compression can be caused by spasm of the piriformis muscle.
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Piriformis syndrome usually starts with pain, tingling, or numbness in the buttocks. Pain can be severe and extend down the length of the sciatic nerve (called sciatica). The pain is due to the piriformis muscle compressing the sciatic nerve, such as while sitting on a car seat or running. Pain may also be triggered while climbing stairs, applying firm pressure directly over the piriformis muscle, or sitting for long periods of time. Most cases of sciatica, however, are not due to piriformis syndrome.
Piriformis Syndrome Diagnosis
There is no definitive test for piriformis syndrome. In many cases, there is a history of trauma to the area, repetitive, vigorous activity such as long-distance running, or prolonged sitting. Diagnosis of piriformis syndrome is made by the patient’s report of symptoms and by physical exam using a variety of movements to elicit pain to the piriformis muscle. In some cases, a contracted or tender piriformis muscle can be found on physical exam.
Because symptoms can be similar in other conditions, radiologic tests such as MRIs may be required to rule out other causes of sciatic nerve compression, such as a herniated disc.