0 relating to the area between the sacrum (= a bone at the base of the back) and the thin, pointed, sticking out part of the ischium (= the lower pelvic bone):
the sacrospinous ligament
The sacrotuberous and sacrospinous ligaments (also known as the extrinsic sacroiliac joint ligaments) limit the amount the sacrum flexes.
And, lastly, some fibers of the sacrospinous and sacrotuberous ligaments (arising from the spine of the ischium and the ischial tuberosity respectively) also attach to the coccyx.
