Interosseous sacroiliac ligament

The Interosseous Sacroiliac Ligament lies deep to the posterior ligament, and consists of a series of short, strong fibers connecting the tuberosities of the sacrum and ilium. The major function of the interosseous sacroiliac ligament is to keep the sacrum and ilium together and therefore prevent abduction or distraction of the sacroiliac joint. This is performed by the nearly horizontal direction of the fibers running perpendicular from the sacrum to the ilium.