Nerve to Obturator Internus and Superior Gemellus Muscles, Posterior View

Description

Arising from the anterior rami of L5, S1, and S2 within the sacral plexus, the nerve to obturator internus is traced posteriorly across the pelvic wall before it reaches the lesser sciatic foramen. Its fibers course inferior to the piriformis and in close relationship to the ischial spine and sacrospinous ligament, then turn laterally toward obturator internus on the pelvic surface of the obturator membrane. A muscular branch is shown continuing to the superior gemellus, which sits superior to obturator internus and deep to the gluteus maximus at the posterior hip. Bony landmarks such as the sacrum, ilium, and proximal femur anchor the pathway in anatomic position. Posterior visualization of this nerve matters because it is one of the few pelvic motor nerves that exits the pelvis and re-enters the perineal region, making its course around the ischial spine a reliable teaching landmark and a surgical hazard. Entrapment or iatrogenic injury near the lesser sciatic notch can contribute to deep gluteal pain and impaired external rotation at the hip, and it can be mistaken for sciatica when symptoms overlap in the buttock. It also clarifies the neighborhood of the pudendal nerve and internal pudendal vessels at the ischial spine. Small target, big consequences. Use this artwork for gross anatomy teaching of the sacral plexus, for surgical anatomy references in approaches to the posterior hip, pelvic sidewall, or pudendal canal region, and for figure placement in texts discussing deep gluteal syndrome and posterior pelvic neuropathies. It also supports radiology and pain medicine education when correlating posterior pelvic landmarks with injection or decompression planning. Anatomical accuracy verified by SciePro's Medical Advisory Board.