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Sacroiliac Joint

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Illustration of the sacroiliac joint[1]
Illustration of the sacroiliac joint with labeled ligaments[2]


  • Large, auricular-shapred, diarthrodial synovial joint
  • Largest axial joint in the body
  • Formed by the interaction of the Sacum and Ilium
  • Roughly anterior 1/3 of these two bones represents articulation


  • The rest is composed of complex set of ligamentous connections
    • Primarily: anterior and posterior interosseous ligaments
    • Accessory iliolumbar, sacrotuberous, and sacrospinous ligaments
  • Ligamentous stability
    • Stabilized by posterior sacroiliac ligament, sacrospinous ligament, sacrotuberous ligament
    • Cephalad portion of the posterior joint contains the interosseous ligament and is not a true joint capsule

Muscular support


  • Primary action is stability of trunk and lower extremities
    • Transfer of load between trunk and lower extremities
  • Limits rotation in the transverse axis
  • Facilitates parturition (child birth)
  • Limited mobility, allowing for only about 2 degrees of motion in each plane[3]

Vascular Supply


  • Somewhat controversial
  • Lateral branches of dorsal rami of L4-S3

Clinical Significance

See Also


  1. Image courtesy of https://teachmeanatomy.info/, "The Sacroiliac Joint"
  2. Image courtesy of https://3dmusclelab.com/, "Exploring The Sacroiliac Joint
  3. Vlemming A, Schuenke MD, Masi AT, et al. The sacroiliac joint: an overview of its anatomy, function and potential clinical implications. J. Anat. 2012; 221:537–67.
Created by:
John Kiel on 2 June 2020 22:14:49
Last edited:
12 May 2024 17:10:07