Inferior gemellus muscle

At a glance

English

Inferior gemellus muscle

Latin (TA2)

Musculus gemellus inferior

System

Muscle

Region

Lower limb

Side

Paired, left and right

About the inferior gemellus muscle

The inferior gemellus is one of a pair of small twin muscles, the gemelli, lying deep in the buttock alongside the tendon of obturator internus. Its name is the diminutive of the Latin for twin. The gemelli belong to the short lateral rotators of the hip, a deep group that also includes piriformis, obturator internus, obturator externus and quadratus femoris.

Its origin is the top of the ischial tuberosity, just below the groove where the obturator internus tendon bends round the lesser sciatic notch. Its fibres run outwards along the lower edge of that tendon, blend with it, and end with it on the inner face of the greater trochanter, in front of the trochanteric fossa. The superior gemellus does the same along the tendon's upper edge, from the ischial spine, so the obturator tendon lies in a groove between the two. The inferior muscle is usually the larger and is rarely absent. Below it lies quadratus femoris.

Together with obturator internus, the gemelli rotate the extended thigh laterally and help abduct the thigh when the hip is bent. Their more constant role is to keep the head of the femur firmly in its socket, acting like a short rotator cuff of the hip. They also add power to obturator internus, whose pull is weakened as its tendon turns sharply round the bone.

The inferior gemellus shares its nerve with quadratus femoris, whereas the superior gemellus is supplied with obturator internus. Both gemelli receive blood mainly from the inferior gluteal and medial circumflex femoral arteries. In the posterior approach to the hip, surgeons detach and later repair these short rotators, and the sciatic nerve runs across their back surface, so it must be protected.

Attachments, action and supply

Origin

Top of the ischial tuberosity, below the groove for the obturator internus tendon.

Insertion

Inner face of the greater trochanter, blended with the obturator internus tendon.

Action

Laterally rotates the extended thigh and abducts the flexed thigh with obturator internus; keeps the head of the femur seated in its socket.

Nerve supply

Nerve to quadratus femoris (L4, L5, S1).

Blood supply

Inferior gluteal artery and medial circumflex femoral artery.