Muscles

Obturator Internus Muscle

• A flat, fan-shaped muscle that originates from the deep surface of the obturator membrane and from associated regions of the pelvic bone that surround the obturator foramen, it inserts on the greater trochanter of the femur.

• It forms a large part of the antero-lateral wall of the pelvic cavity.

• It laterally rotates the femur during hip extension and abduct the femur during hip flexion. It also helps to steady the femoral head in the acetabulum

Piriformis muscle

• A triangle shaped muscle that originates in the bridges of bone between the four anterior sacral foramina, it inserts on the greater trochanter of the femur above the insertion of the obturator internus muscle.

• It forms a large part of the posterolateral wall of the pelvic cavity.

• It is an external rotator of the hip. It rotates the femur during extension of the hip and abducts the femur during flexion of the hip.

Coccygeus muscle

• A triangle shaped muscle that lies parallel to the inferior border of the piriformis muscle. It originates from the tip of the ischial spine and inserts into the lateral margin of the coccyx.

• It helps support the pelvic viscera and to flex the coccyx.

Levator ani muscles (iliococcygeus, pubococcygeus and puborectalis muscles)

• The levator ani muscles are a group of muscles that act as supporting structures in urinary control.