The posterior border of the ala, shorter than the anterior, also presents two projections separated by a notch, the posterior superior iliac spine and the posterior inferior iliac spine. The posterior superior iliac spine serves for the attachment of the oblique portion of the posterior sacroiliac ligaments and the Multifidus.

External links

• - "Posterior view of the skeleton of the trunk."
• - "The Female Pelvis - bones"
• - "The Sacral and Coccygeal Vertebrae, Posterior View"