Muscle · Lower limb
Superior gemellus: origin, insertion, action and innervation
The superior gemellus runs from the ischial spine to the greater trochanter of the femur. It laterally rotates the hip and has the nerve to obturator internus.
Quick answer
- Latin name
- Musculus gemellus superior
- Origin
- Outer surface of the ischial spine of the hip bone
- Insertion
- Medial surface of the greater trochanter of the femur, through the tendon of the obturator internus
- Action
- Laterally rotates the extended hip; helps abduct the flexed hip; steadies the head of the femur in the acetabulum
- Innervation
- Nerve to obturator internus (L5-S2)
- Blood supply
- Inferior gluteal artery, with small branches of the internal pudendal artery
See it on the 3D body
The superior gemellus lit on the 3D hip and thigh, as in the hip and thigh quiz. Turn the body, peel the layers, tap any structure for its name.
The superior gemellus is a thin muscle at the back of the hip that runs from the ischial spine to the greater trochanter of the femur, along the upper edge of the obturator internus tendon. It laterally rotates the extended thigh and is supplied by the nerve to obturator internus (L5-S2).
Where it is
The superior gemellus lies deep in the buttock, under the gluteus maximus. It is the second muscle in the row of short lateral rotators: the piriformis lies just above it, and the tendon of the obturator internus lies just below it. Its twin, the inferior gemellus, runs along the lower edge of the same tendon.
The superior gemellus is usually the smaller of the two twins, and it is occasionally absent. It sits at the level of the lesser sciatic foramen, the opening through which the obturator internus tendon leaves the pelvis. The sciatic nerve usually appears at the lower border of the piriformis and then runs down over the back of the superior gemellus, so this muscle is a useful landmark when you trace the nerve. See the deep layer on muscles of the hip.
Origin and insertion
- Origin: the outer (gluteal) surface of the ischial spine, the pointed projection between the greater and lesser sciatic notches of the hip bone.
- Insertion: it fuses with the upper border of the obturator internus tendon and reaches, through it, the medial surface of the greater trochanter of the femur.
The two gemelli and the obturator internus are often described together as a single unit, the triceps coxae, because they share one tendon on the femur.
What it does
- Lateral rotation of the extended hip: it turns the thigh outward, helping the obturator internus, which does most of the work in this unit.
- Abduction of the flexed hip: with the hip bent, its pull helps move the thigh away from the midline.
- Joint stability: lying on the back of the hip joint capsule, it helps keep the head of the femur centered in the acetabulum.
It is a helper rather than a prime mover. Most of the force of the triceps coxae comes from the obturator internus, and the gemelli add to it.
Innervation and blood supply
The superior gemellus receives the nerve to obturator internus (L5-S2), a branch of the sacral plexus. The nerve leaves the pelvis through the greater sciatic foramen, gives a twig to the superior gemellus, then curves around the ischial spine to reach the obturator internus inside the pelvis.
Its blood comes mainly from the inferior gluteal artery, with small contributions from nearby branches of the internal pudendal artery.
How to remember it
- "Superior sticks to the spine": the superior gemellus starts on the ischial spine, the inferior gemellus on the ischial tuberosity below.
- Upper twin, upper nerve: the nerve to obturator internus passes the superior gemellus on its way around the ischial spine and gives it a twig. The lower twin gets the nerve to quadratus femoris instead.
- Triceps coxae: three bellies, one tendon, like a small triceps at the hip (coxa is Latin for hip).
- Under the piriformis: if you can find the piriformis, the next muscle down is the superior gemellus.
Test yourself in the hip and thigh quiz.
Frequently asked questions
What is the action of the superior gemellus?
It laterally rotates the extended thigh, helps abduct the flexed thigh and steadies the hip joint.
Which nerve supplies the superior gemellus?
The nerve to obturator internus, from roots L5 to S2.
What is the difference between the superior and inferior gemellus?
The superior gemellus arises from the ischial spine and is supplied by the nerve to obturator internus. The inferior gemellus arises from the ischial tuberosity and is supplied by the nerve to quadratus femoris.
What is the triceps coxae?
A name for the obturator internus and the two gemelli together, since all three insert by one tendon on the greater trochanter.
