Nerve to the Quadratus Femoris and Inferior Gemellus, Posterior View

Description

Arising from the anterior divisions of L4 to S1 within the sacral plexus, the nerve to quadratus femoris courses inferiorly and laterally across the pelvic surface of the ischium toward the deep gluteal region. From a posterior pelvis view, the sacrum and posterior iliac bones frame the exiting lumbosacral trunks and sacral nerve roots, with the sciatic nerve forming as a thick cord that descends inferior to the piriformis. The nerve to quadratus femoris runs deep and anterior to the sciatic nerve, passing toward the ischial spine and lesser sciatic notch, then continuing to the posterior aspect of the hip joint capsule before entering quadratus femoris; a small branch to the inferior gemellus typically diverges near the tendonous interval just inferior to the obturator internus. This is the branch you need when teaching deep gluteal anatomy beyond the “big three” structures. Its relationship to the ischium and the short external rotators matters in posterior hip exposures and in understanding deep gluteal syndrome, where symptoms can mimic sciatica but the pain generator lies in the short rotators or adjacent fibrous bands rather than the sciatic nerve itself. Iatrogenic injury is uncommon but real during posterior approaches to the hip and during procedures that work close to the ischial spine, including some sciatic nerve decompressions and deep injections aimed too medially. Use this artwork in anatomy lab manuals, orthopedic and sports medicine teaching decks, or a surgical atlas page on the posterior approach to the hip where clear separation of the sciatic nerve from the nerve to quadratus femoris prevents students from “overcalling” every posterior nerve as sciatic. It also fits neuraxial and peripheral nerve block education when discussing why certain posterior hip pain patterns do not follow a clean dermatomal map. Anatomical accuracy verified by SciePro's Medical Advisory Board.