Piriformis is one of the muscles of the gluteal region. It is located both within the pelvis and posterior to the hip joint.
It originates from the second to fourth lateral masses of the sacrum on its anterior surface and the adjoining sacrotuberous ligament. It passes laterally to exit the pelvis through the greater sciatic foramen. Lying posterior to the femoral head, it inserts into the superior and medial border of the greater trochanter of the femur.
It is innervated by the anterior primary rami of S1 and S2.
Piriformis has many functions:
- lateral rotation of the thigh in the extended position
- abduction of the flexed thigh
- stabilization of the hip joint