Where does obturator internus arise?

Where does obturator internus arise?

• A. Sacrum
• B. Pubis
• C. Obturator membrane
• D. Iliac fossa

Answer: (C)

The key idea is the muscle’s origin on the pelvic sidewall. Obturator internus begins from the internal surface of the obturator membrane and the surrounding margins of the obturator foramen in the pelvis. From there it passes through the lesser sciatic foramen to insert on the greater trochanter of the femur, acting as a lateral rotator of the thigh. This makes the obturator membrane the best answer because it precisely defines the anatomical starting point of the muscle. The sacrum is associated with muscles like the piriformis, the iliac fossa is the origin for iliacus, and while the pubic rami contribute to the margins of the obturator foramen, the specific origin of obturator internus is the obturator membrane itself.

The key idea is the muscle’s origin on the pelvic sidewall. Obturator internus begins from the internal surface of the obturator membrane and the surrounding margins of the obturator foramen in the pelvis. From there it passes through the lesser sciatic foramen to insert on the greater trochanter of the femur, acting as a lateral rotator of the thigh. This makes the obturator membrane the best answer because it precisely defines the anatomical starting point of the muscle. The sacrum is associated with muscles like the piriformis, the iliac fossa is the origin for iliacus, and while the pubic rami contribute to the margins of the obturator foramen, the specific origin of obturator internus is the obturator membrane itself.