Anatomy of Piriformis Muscle and Sciatic Nerve

Information: Piriformis Syndrome and Sciatica Anatomy

This drawing illustrates the important anatomy for piriformis syndrome.

The nerve-related leg pain of Sciatica is often due to piriformis muscle syndrome. Unlike the sciatica from a herniated disk, there is often little or no back pain while buttock pain predominates. The pain is worse when sitting, relieved by standing or walking, and often extends no farther down the leg than the ankle or mid-foot. When toes are involved, it usually affects all five toes.

This drawing illustrates the important anatomy for piriformis syndrome and shows how certain leg positions pull the piriformis muscle up against the sciatic nerve causing buttock pain and radiating leg pain.

Physical Exam Findings and Key Symptoms

Information: Piriformis Syndrome Physical Exam

Animation:  Critical physical exam for muscle based piriformis syndrome.

The patient's foot is placed lateral to the contralateral knee. Resisted abduction or adduction against the examiner's hand may reproduce the symptoms. Straight leg raising is typically negative.

There is often relief obtained by traction on the involved leg, particularly by pulling upwards at a ten to twenty degree angle and towards the contralateral side by a similar amount. The distribution of symptoms typically involves both L5 (big toe) and S1 (small toe) components because this a pan-sciatic syndrome. The symptoms often progress no further than the ankle in distinction to sciatica from a lumbar disk which typically radiates into the toes.

Image Anatomy for Injections

Information: Anatomy of the piriformis muscle and sciatic nerve in a T1 weighted axial MRI scan

Animation: This T1 weighted axial MRI scan shows the anatomy used to guide the injection of the piriformis muscle in an Open MRI scanner.