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Lesser Sciatic Foramen Space

spatium foraminis ischiadici minoris

The lesser sciatic foramen is bounded by the lesser sciatic notch of the ischium, the sacrospinous ligament superiorly, and the sacrotuberous ligament posteriorly. The obturator internus muscle and tendon, the nerve to obturator internus, and the pudendal nerve and internal pudendal vessels pass through this foramen between the pelvis and the ischioanal fossa.

Region: Pelvis & Hip

Clinical Relevance

Clinical Notes

The lesser sciatic foramen is the anatomical basis for the pudendal nerve block, where the pudendal nerve is anaesthetised as it curves around the ischial spine adjacent to the foramen. Pudendal neuralgia involves compression of the pudendal nerve at or near this foramen, producing perineal pain and bladder dysfunction. The obturator internus tendon uses this foramen as a pulley, changing direction from the lateral pelvic wall to the greater trochanter.

Pathology

Common Injuries & Conditions

Pudendal Nerve Entrapment

Compression of the pudendal nerve in or near the lesser sciatic foramen between the sacrospinous and sacrotuberous ligaments, producing chronic perineal pain, dyspareunia, and voiding dysfunction, managed by CT-guided nerve block or surgical decompression.