Myofascial pain patterns of the piriformis muscle

Symptoms of the piriformis syndrome may be caused by (1) referral of pain from trigger points in the muscle, (2) by neurovascular entrapment at the greater sciatic notch, and (3) by sacroiliac joint dysfunction. Essential (solid red) and spillover (stippled red) referred pain from piriformis trigger points (x's) projects primarily to the sacroiliac region, the buttock, and the hip joint posteriorly, and sometimes also extends over the proximal two thirds of the posterior thigh. But much of the radiating pain of the piriformis muscle is caused by entrapment of neurovascular structures as they pass through the greater sciatic foramen. (From Travell JG, Simon DG. Myofascial origins of low back pain. Volume 2. Piriformis and other short lateral rotators. Postgrad Med 1992;73:188, with permission.)