Dr. Ebraheim’s educational animated video describes the anatomy of the superior and inferior gemellus muscels- lateral external rotator of the hip.
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The Gemelli are two small muscles which are part of the six lateral external rotators of the hip. The superior gemellus muscle arises from the ischial spine. The inferior gemellus muscle arises from the posterior portion of the ischial tuberosity and the lateral obturator ring. Both muscles are inserted into the medial surface of the greater trochanter of the femur in a common insertion site and tendon with the obturator internus. The superior gemellus muscle innervates to the obturator internus. The inferior gemellus muscle innervates to the quadratus femoris. All lateral rotators of the hip are supplied by the sacral plexus except for the obturator externus which is supplied by the posterior division of the obturator nerve. The arrangement of the muscles is the piriformis, the superior gemellus, the obturator internus, the inferior gemellus, obturator externus, and the quadratus femoris. The Gemelli are supplied by the nerve with the same name as the muscle below it. Obviously, it is the nerve, and not the muscles that gives the innervation. The obturator externus muscle is far away from the Gemelli and has a different nerve supply than the other muscles, so we are not using the obturator externus nerve, instead we are using the quadratus femoris nerve to supply the inferior gemellus muscle. The obturator externus is supplied by the posterior branch of the obturator nerve which is different from the nerve supply of the Gemelli muscles. The superior and inferior gemellus muscles both rotate the thigh laterally.