Obturator externus muscle

Last revised by Craig Hacking on 14 Mar 2025

The obturator externus is a flat, triangular muscle, which covers the outer surface of the anterior wall of the pelvis.

Summary

  • Origin: external surface of obturator membrane and adjacent bone (inferior pubic ramus and the ramus of the ischium)

  • Insertion: trochanteric fossa of femur

  • Blood supplyobturator and medial circumflex femoral arteries

  • Innervation: Posterior division of obturator nerve (L3, L4)4

  • Action: thigh external rotation, stabilization of hip joint

Gross Anatomy

The obturator externus is a triangular muscle arising from the antero-lateral two thirds of the external surface of the obturator membrane. It passes laterally and posteriorly, beneath the neck of femur, narrowing into a tendon which inserts into the trochanteric fossa of the femur4.

The posterior aspect of the hip joint capsule extends along the neck of femur only as far as where the obturator externus tendon is in contact with the periosteum. While the anterior aspect of the joint capsule includes the whole neck of femur3.

The anterior division of the obturator nerve reaches the thigh by coursing in front of the obturator externus muscle belly. The posterior branch of the obturator nerve pierces the upper border of the muscle belly, giving off a branch to supply the muscle3,4.

Posterior to the muscle lie the obturator vessels, sandwiched between the muscle belly and obturator membrane3.

Cases and figures

  • Figure 1: Gray's illustration
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