Quick Facts
Origin: Internal surface of obturator membrane and adjacent bones.
Insertion: Medial aspect of greater trochanter of femur.
Action: Laterally rotates and transversely abducts thigh at hip joint.
Innervation: Nerve to obturator internus (L5-S1).
Arterial Supply: Internal pudendal and obturator artery.
Related parts of the anatomy
Origin
The obturator internus muscle originates from the:
- internal surface of obturator membrane;
- internal aspect of the bony margin of the obturator foramen;
- lateral wall of lesser pelvis.
Insertion
The fibers of the obturator internus muscle travel posterolaterally and insert, via a tendon that blends with the tendons of the superior and inferior gemelli, onto the medial aspect of the greater trochanter of the femur.
Key Features & Anatomical Relations
The obturator internus muscle is one of the deep gluteal muscles. It is a broad, multipennate type of skeletal muscle. Within the lesser pelvis, the fibers of the obturator internus muscle converge as they travel posterolaterally to the lesser sciatic foramen. As it passes through the foramen, and enters the gluteal region, the muscle hooks around the lesser sciatic notch and then changes its line of pull to a more lateral direction. As it travels posterior to the hip joint, the muscle belly gives rise to a flat tendon that travels laterally to its insertion site.
The obturator internus muscle is located:
- superficial to the capsule of the hip joint, and the sciatic bursa of obturator internus muscle;
- deep to the obturator fascia, the gluteus maximus muscle, and the sciatic nerve;
- superior to the inferior gemellus muscle;
- inferior to the superior gemellus muscle;
- medial to the urinary bladder and the ischioanal fossa.
Actions & Testing
The obturator internus, superior gemellus and inferior gemellus muscles work as a unit, collectively known as the triceps coxae, and are involved in multiple actions:
- laterally rotate the thigh at the hip joint;
- transversely abduct the thigh at the hip joint (i.e., they abduct the flexed thigh along the transverse plane).
The obturator internus muscle cannot be tested in isolation, therefore all three muscles of the triceps coxae are tested simultaneously by transversely abducting the thigh at the hip joint against resistance (Standring, 2016).
References
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.
