Superior gemellus muscle

At a glance

English

Superior gemellus muscle

Latin (TA2)

Musculus gemellus superior

System

Muscle

Region

Lower limb

Side

Paired, left and right

About the superior gemellus muscle

The superior gemellus is a thin, narrow muscle in the deep gluteal region, one of a pair of small twins that flank the tendon of obturator internus. Its name comes from the Latin for a little twin. It lies between piriformis above and the obturator internus tendon below, with the inferior gemellus on the other side of the tendon. It is the smaller of the two gemelli and is sometimes absent.

Its origin is the gluteal (outer) face of the ischial spine, at the upper edge of the lesser sciatic notch. Its fibres run outwards horizontally along the upper border of the obturator internus tendon and blend with it, so the gemelli and the tendon form a three-part muscle. Their combined insertion is the inner face of the greater trochanter, just above the trochanteric fossa. In some people the fibres extend separately to the trochanter itself.

The superior gemellus helps obturator internus rotate the extended thigh outwards and abduct the thigh when the hip is flexed. With the other short rotators it holds the femoral head firmly into the acetabulum. The gemelli add power where the obturator tendon has to change direction sharply around the lesser sciatic notch and is therefore at a mechanical disadvantage.

It is supplied by the nerve to obturator internus, a sacral plexus branch that also serves the larger muscle, whereas the inferior gemellus takes its nerve from the branch to quadratus femoris. Blood comes from the inferior gluteal artery, with help from the internal pudendal artery. The sciatic nerve runs down across its back after leaving the pelvis below piriformis, so the muscle is a landmark in posterior hip surgery, where the short rotators are detached and later repaired.

Attachments, action and supply

Origin

Outer (gluteal) face of the ischial spine.

Insertion

Inner face of the greater trochanter, through the tendon of obturator internus.

Action

Assists obturator internus in laterally rotating the extended thigh and abducting the flexed thigh; helps stabilise the femoral head.

Nerve supply

Nerve to obturator internus (L5, S1, S2).

Blood supply

Inferior gluteal artery, with branches of the internal pudendal artery.