Full Piriformis Muscle Description
[Continued from above] . . . 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.
Prepared by Tim Taylor, Anatomy and Physiology Instructor