The piriformis muscle, whose name means “pear-shaped,” is a deep muscle of the gluteal region. It is the most superior muscle in a group of six muscles that work together to rotate the thigh laterally at the hip joint and to abduct the thigh as well.
The piriformis muscle is found in the gluteal region deep to the gluteus maximus and inferior to the gluteus minimus. Its origins are spread along the anterior region of the sacrum. From the sacrum it extends laterally, passing through the greater sciatic foramen and crossing the hip joint. As the piriformis muscle approaches its insertion on the greater trochanter of the femur, it gradually tapers to a point, giving it a pear-like shape.
Working together with the superior gemellus, inferior gemellus, obturator internus, obturator externus, and quadratus femoris muscles, the piriformis acts as an external rotator of the thigh. It achieves this action by pulling the greater trochanter posteriorly, turning the thigh so that the knee and anterior thigh point away from the opposite leg. These muscles also act as abductors of the thigh by pulling the greater trochanter closer to the body’s midline and consequently moving the distal portion of the thigh away from the midline.