Sacrotuberous and sacrospinous ligaments attach sacrum to

The sacrotuberous ligament is a strong broad band of fibrous tissue. It has broad upper end and narrow lower lateral end.Upper end is attached from above downward to posterior superior iliac spine, posterior inferior iliac spine, lower pa of posterior surface and lateral border of sacrum and adjoining pa of coccyx. The lower end is attached to medial margin of ischial tuberosity. Some of the fibres from lower end continue on to the ramus of ischium as the falciform process.The sacrospinous ligament is a triangular sheet of fibrous tissue with its apex attached laterally to the ischial spine and base medially to the side of sacrum and coccyx.The sacrospinous and sacrotuberous ligaments conve the greater and lesser sciatic notches of the hip bone into greater and lesser sciatic foramina-the two impoant exits from the pelvis.Reference: Textbook of anatomy, Abdomen and Lower limb, Vishram Singh, 2nd edition, page no.204