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Obturator Internus Muscle Anatomy

The obturator internus muscle is located partly in the pelvis, where it covers most of the lateral wall of the lesser pelvis. It leaves the pelvis through the lesser sciatic foramen, makes a right-angle turn, becomes tendinous, and receives the distal attachments of the gemelli before attaching to the medial surface of the greater trochanter (trochanteric fossa) of the femur.

There are six lateral rotators of the thigh: piriformis, obturator internus, superior and inferior gemelli, quadratus femoris, and obturator externus. These muscles also stabilize the hip joint.

The obturator internus and the superior and inferior gemelli (L. geminus, small twin) form a tricipital (three-headed) muscle, the triceps coxae (triceps of the hip), which occupies the gap between the piriformis and the quadratus femoris. The common tendon of these muscles lies horizontally in the buttocks as it passes to the greater trochanter of the femur.

See Also: Obturator Externus Muscle Anatomy

Obturator Internus Muscle Anatomy

The obturator internus has 2 sites of origin. It originates from both the posterior surface of the obturator membrane and the rami surrounding the obturator foramen and inserts onto the greater trochanter of the femur

This muscle receives blood supply from branches of the obturator artery, the gluteal artery, and the pudendal artery. It’s innervated by the nerve to the obturator internus. This is a branch of the sacral plexus and originates from the L5-S2 spinal nerves.

See Also: Hip Joint Anatomy

The obturator internus muscle function to external rotate and abduct the hip, it also has a critical function of stabilization of the hip joint. The obturator internus shortens as the hip moves from flexion to extension, which indicates that it provides support to the hip joint during weight-bearing and propulsion activities. It has been well established that the obturator internus is a “postural muscle” that holds the femoral head in the acetabulum.

The bursa of the obturator internus muscle allows free movement of the muscle over the posterior border of the ischium, where the border forms the lesser sciatic notch and the trochlea over which the tendon glides as it turns.

Obturator Internus Muscle
OriginInternal surface of obturator membrane and posterior bony margins of obturator foramen
InsertionMedial surface of greater trochanter of femur, in common with superior and inferior gemelli
InnervationNerve to the obturator internus and superior gemellus, a branch of the sacral plexus (L5, S1)
Blood SupplyObturator artery, internal pudendal and superior and inferior gluteal arteries
ActionRotates the femur laterally (external rotation)
Helps abduct the thigh when it is flexed
Stabilize the hip joint

References & More

  1. Gray’s Anatomy: The Anatomical Basis of Clinical Practice
  2. Clinically Oriented Anatomy – 8th Edition
  3. Larson MR, Ryan W. Anatomy, Abdomen and Pelvis, Obturator Muscles. [Updated 2023 Jan 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: Pubmed
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