Anatomy of the SI Joint
The sacroiliac joint (SIJ) is made up of 3 bones: 2 inominates and the sacrum that connect the spine to the pelvis. The inominate bones are comprised of a fused ilium, ischium, and pubis that conjoin at the acetabulum of the pelvis. The head of the femur sits in the acetabulum to form the hip joint, and each inominate bone articulates with the sacrum, to form the sacroiliac joint. The sacrum is made up of 5 fused vertebrae that form an auricular C-shape. The purpose of the sacrum is to provide stability to the pelvis and assist in transmitting the weight from the body to the pelvis. In addition to bony structures, many ligaments play a role in the overall pelvic stability, three main ligaments being the iliolumbar, sacrotuberous, and sacrospinous which not only play a role in pelvic stability, but sacral stability as well.
The sacroiliac joint (SIJ) is made up of 3 bones: 2 inominates and the sacrum that connect the spine to the pelvis. The inominate bones are comprised of a fused ilium, ischium, and pubis that conjoin at the acetabulum of the pelvis. The head of the femur sits in the acetabulum to form the hip joint, and each inominate bone articulates with the sacrum, to form the sacroiliac joint. The sacrum is made up of 5 fused vertebrae that form an auricular C-shape. The purpose of the sacrum is to provide stability to the pelvis and assist in transmitting the weight from the body to the pelvis. In addition to bony structures, many ligaments play a role in the overall pelvic stability, three main ligaments being the iliolumbar, sacrotuberous, and sacrospinous which not only play a role in pelvic stability, but sacral stability as well.
References:
1. http://www.becomehealthynow.com/popups/sacrum_pelvis1.htm
2. Dutton, M. (2008). Orthopaedic Examination Evaluation and Intervention. New York: McGraw-Hill Companies, Inc.
3. Zelle, B.A., Gruen, G.S., Brown, S., George, S. (2005). Sacroiliac Joint Dysfunction: Evaluation and Management. Clinical Journal of Pain, 21(5): 446-455.
1. http://www.becomehealthynow.com/popups/sacrum_pelvis1.htm
2. Dutton, M. (2008). Orthopaedic Examination Evaluation and Intervention. New York: McGraw-Hill Companies, Inc.
3. Zelle, B.A., Gruen, G.S., Brown, S., George, S. (2005). Sacroiliac Joint Dysfunction: Evaluation and Management. Clinical Journal of Pain, 21(5): 446-455.