Anatomy of the sacroiliac joint

The sacroiliac joint, a multiplanar joint located in the dorsal complex of the pelvis, is one of the most important joints in the human to ensure upright and bipedal stability. The joint has been the subject of study for many years, but due to the presence of anatomic variability, challenges remain when analyzing its biomechanics in both normal and pathologic states. The joint is well vascularized and heavily innervated, making it a clinically significant structure with respect to primary, autoimmune, and traumatic disease processes. The chapter describes the gross anatomy of this joint as well as its embryologic origins, variability, and proposed movements as it relates to the joint’s potential for pathogenicity. This information will be useful to clinicians during diagnosis and radiographic evaluation of the patient with low back pain.