The piriformis is one of the deep muscles within the gluteal region. It forms the anterolateral wall of the pelvic cavity and the lateral wall of the ischio-anal fossa in the perineum. The tendon forms a 90 degree bend around the ischium, passing between the ischial spine and ischial tuberosity passing posteroinferior to the hip joint to attach to the greater trochanter of the femur below the insertion of the piriformis.
The gluteal region consists of two groups of muscles:
- Deep group: small muscles which mainly laterally rotate the femur at the hip joint. These include the piriformis, obturator internus, gemellus superior, gemellus inferior, and quadratus femoris.
- Superficial group: larger muscles which cause abduction and extension of the femur at the hip joint. These include the gluteus maximus, gluteus medius, gluteus minimis and the tensor fascia latae.
- Lateral rotation of hip
- Assists abduction of hip when hip is flexed
- Nerve to the obturator internus and superior gemellus; L5,S1 (branch of the sacral plexus)
- Internal pudendal artery
- Superior and inferior gluteal arteries