The sacrotuberous ligament (Fig. 1) originates from the dorsal surface of the sacrum and coccyx and from the posterior and inferior iliac spine, passing inferiorly and laterally to the medial surface of the ischiotuberosity. It helps form the medial margin of the greater and lesser sciatic foramen.
( Fig. 1) Pelvic ligaments, external view from posterior. Visible are the sacrotuberous and sacrospinous ligaments, as well as the sciatic, superior gluteal, posterior femoral cutaneous, and pudendal nerves.
The sacrospinous ligament (see Fig. 1) originates from the lateral margin of the coccyx and the lowermost portion of the sacrum and attaches to the ischial spine. The greater and lesser sciatic foramina are located superiorly and inferiorly to the sacrospinous ligament. The greater sciatic foramen is superior to the pelvic diaphragm, whereas the lesser is located inferiorly. As a result, structures passing to the perineum and ischiorectal fossa initially travel through the greater sciatic foramen and reemerge through the lesser. The pudendal nerve and artery are dorsal and posterior to the sacrospinous ligament and are seen just medial to the ischial spine. The sciatic nerve is similarly located but is lateral to the ischial spine. It is for this reason that surgical fixation of the vagina to the sacrospinous ligament is performed approximately 2 to 3 cm medial to the ischial spine. The coccygeus muscle is located anterior to the sacrospinous ligament and the fibers of both structures are intimately adherent.