The gemellus inferior is the lower flanking muscle of the obturator internus tendon, originating from the ischial tuberosity. It shares its nerve supply with the quadratus femoris from the nerve to quadratus femoris rather than the obturator internus nerve that supplies the gemellus superior, reflecting their different embryological origins despite their similar mechanical roles. Both gemellus muscles supplement the obturator internus as it turns around the lesser sciatic notch.
| Origin | Upper part of the ischial tuberosity |
|---|---|
| Insertion | Medial surface of the greater trochanter via the obturator internus tendon |
| Nerve Supply | Nerve to quadratus femoris (L4, L5, S1) |
| Blood Supply | Inferior gluteal artery |
| Actions | External rotation of the hip; Compresses the posterior hip capsule |
|---|
Working with the gemellus superior and obturator internus to produce external rotation of the hip, the gemellus inferior adds mechanical reinforcement to the lateral obturator internus tendon pull on the greater trochanter.
The gemellus inferior, like the superior, is assessed as part of the deep external rotator group and is rarely isolated clinically. Proximal hamstring avulsion injuries involving the ischial tuberosity may involve the gemellus inferior origin given its attachment to the upper ischial tuberosity adjacent to the hamstring origins.
Not directly palpable individually. Assessed as part of the posterior hip deep rotator group.
Injury to the gemellus inferior at the ischial tuberosity origin producing deep buttock pain near the hamstring origin, requiring MRI to distinguish from proximal hamstring avulsion.
