Behind the iliac fossa on the internal surface of ala of ilium is a rough surface, the sacropelvic surface, divided into two portions, an anterior and a posterior.
- The anterior surface is the auricular surface, so called from its resemblance in shape to the ear, is coated with cartilage in the fresh state, and articulates with a similar surface on the side of the sacrum.
- The posterior portion, known as the iliac tuberosity, is elevated and rough, for the attachment of the posterior sacroiliac ligaments and for the origins of the Sacrospinalis and Multifidus.
Below and in front of the auricular surface is the preauricular sulcus, more commonly present and better marked in the female than in the male; to it is attached the pelvic portion of the anterior sacroiliac ligament.
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).