Lower limb

Obturator internus

Musculus obturatorius internus

Origin

Inner surface of the obturator foramen and the surrounding pelvic wall (hip bone)

Insertion

Trochanteric fossa of the femur, via a tendon that bends around the lesser sciatic notch

Function

External rotation of the hip in extension, abduction of the hip in 90° flexion; stabilizes the femoral head in the acetabulum

Innervation

Nerve to obturator internus (sacral plexus, L5-S2)

Movement & chain

External rotator of the hip in extension and abductor in 90° hip flexion, part of the deep external rotator group together with piriformis and the gemelli.

Palpation

Not directly palpable from the outside, but can be assessed via rectal or vaginal examination as part of pelvic floor evaluation.

Clinical

The muscle lies close to the pelvic floor complex; overuse or trigger points can contribute to pelvic pain and are sometimes mistaken for piriformis syndrome.

Segmental innervation

L5-S2.

In clinical practice

Relevant landmark in pelvic floor physiotherapy; the fascia of this muscle forms the pudendal canal (Alcock's canal), important in pudendal neuralgia.

Region in the model

Lower limb