Obturator internus muscle
The obturator internus and nearby muscles
Coronal section of anterior part of pelvis, through the pubic arch. Seen from in front. (Obturator internus labeled at right.)
Latin	musculus obturatorius internus
Gray's	subject #128 477
Origin	Ischiopubic ramus & obturator membrane
Insertion	medial aspect of the Greater trochanter
Artery	Superior gluteal artery
Nerve	Nerve to obturator internus (L5, S1)
Actions	Abducts & rotates laterally thigh, and stabiliser of the hip during walking

The obturator internus muscle originates on the medial surface of the obturator membrane, the ischium near the membrane, and the rim of the pubis.

It exits the pelvic cavity through the lesser sciatic foramen.

The obturator internus is situated partly within the lesser pelvis, and partly at the back of the hip-joint.

It functions to help laterally rotate extended thigh and abduct flexed thigh, as well as to steady the femoral head in the acetabulum.

[edit] Origin and insertion

It arises from the inner surface of the antero-lateral wall of the pelvis, where it surrounds the greater part of the obturator foramen, being attached to the inferior rami of the pubis and ischium, and at the side to the inner surface of the hip bone below and behind the pelvic brim, reaching from the upper part of the greater sciatic foramen above and behind to the obturator foramen below and in front.

It also arises from the pelvic surface of the obturator membrane except in the posterior part, from the tendinous arch which completes the canal for the passage of the obturator vessels and nerve, and to a slight extent from the obturator fascia, which covers the muscle.

The fibers converge rapidly toward the lesser sciatic foramen, and end in four or five tendinous bands, which are found on the deep surface of the muscle; these bands are reflected at a right angle over the grooved surface of the ischium between its spine and tuberosity.

Muscles of the gluteal and posterior femoral regions.

[edit] Bursa/bands

This bony surface is covered by smooth cartilage, which is separated from the tendon by a bursa, and presents one or more ridges corresponding with the furrows between the tendinous bands.

These bands leave the pelvis through the lesser sciatic foramen and unite into a single flattened tendon, which passes horizontally across the capsule of the hip-joint, and, after receiving the attachments of the gemelli, is inserted into the forepart of the medial surface of the greater trochanter above the trochanteric fossa.

A bursa, narrow and elongated in form, is usually found between the tendon and the capsule of the hip-joint; it occasionally communicates with the bursa between the tendon and the ischium.

[edit] Additional images

Right hip bone. External	Right hip bone. Internal surface.	Right femur. Anterior surface.	Structures surrounding right hip-joint.
Sacral plexus of the right side.

[edit] External links

• -1348861872 at GPnotebook
• LUC obi
• SUNY Labs 13:st-0407 - "Gluteal Region: Muscles"
• SUNY Labs 43:st-0603 - "The Female Pelvis: Muscles"
• Cross section at UV pelvis/pelvis-e12-15
• pelvis at The Anatomy Lesson by Wesley Norman (Georgetown University) (femalepelvicdiaphragm, malepelvicdiaphragm)
• perineum at The Anatomy Lesson by Wesley Norman (Georgetown University) (analtriangle3)
• Int. J. Morphol., 25(1):95-98, 2007

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This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.