Nerve to quadratus femoris and inferior gemellus
The nerve to quadratus femoris and inferior gemellus is formed from the anterior (ventral) divisions of the L4, L5 and S1 nerve roots of the sacral plexus. The nerve supplies the quadratus femoris and inferior gemellus muscles as well as providing an articular branch to the hip joint.
The nerve to quadratus femoris arises from the anterior divisions of the sacral plexus. It is formed from the L4-S1 nerve roots and exits the pelvis via the greater sciatic foramen inferior to the piriformis muscle and deep to the sciatic nerve. The nerve to quadratus femoris, unlike other nerves in the gluteal regions, lies anterior to the plane of the deep muscles of the gluteal region.
It descends along the ischium and passes posterior to the hip joint, to which it sends an articular sensory branch. In this position the nerve lies deep to the tendon of the obturator internus muscle and gemelli which thus separate it from the overlying sciatic nerve.
The nerve continues downwards to pierce the deep (anterior) surface of the quadratus femoris muscle. The nerve also supplies the inferior gemellus muscle.
The nerve to quadratus femoris is separated from the sciatic nerve by the obturator internus and gemelli muscles.
It has been noted in cadaveric studies that the nerve to quadratus femoris and obturator internus frequently arises from a common root and communication between these two nerves has been regularly observed. The inferior gemellus muscle has been recorded to occasionally receive additional innervation by branches of the nerve to obturator internus.