Obuturator internus is one of the muscles of the lateral pelvic wall extending into the gluteal region. It arises from the inner surface of the obturator membrane lining the obturator foramen and the neighbouring surfaces of the pubis and ischium. From this broad surface, it narrows down as it passes posterolaterally to form a tendon that traverses the lesser sciatic foramen. Just inferior to the ischial spine it turns laterally. There is a bursa interposed between the tendon and the bone at this point. Passing laterally, it inserts into medial surface of the greater trochanter of the femur.
The superior and inferior gemelli muscles insert into the tendon of obturator internus. They are sometimes considered as extrapelvic parts of the muscle.
It is innervated by the nerve to obturator internus (L5, S1), a branch of the sciatic nerve.
Obturator internus has several actions:
- stabilise the hip joint
- laterally rotate the flexed thigh
- weakly abducts the flexed thigh