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22 m a s s a g e & b o d y wo r k m ay/ j u n e 2 0 2 2 The sacroiliac (SI) joint is one of the most interesting joints in the body. There actually isn't a single sacroiliac joint, but rather a left and right SI joint. This joint is the articulation on the posterior side of the pelvis between the sacrum and the ilium. The sacrum is essentially a wedge held in place within the pelvic ring to provide stability and allow for a slight degree of movement. Because of the way humans evolved to an upright standing posture, the SI joint has become far more important for weight distribution and mechanics between the upper and lower body. Let's look at some of the more interesting aspects of the structure and function of this unique joint. In children and young adults, the contact surface between the sacrum and ilium is rather smooth and the joint acts like a typical synovial joint. The smooth articular surface and corresponding joint capsule allow for a small amount of movement. As an individual moves into adulthood, the joint surfaces change signifi cantly. The surface of the ilium and sacrum develop ridges and depressions that fi t together more like puzzle pieces. We can infer from this change that as a person ages, stability in the sacroiliac joint becomes more important than mobility. By the eighth decade of life, about 10 percent Current Concepts in Sacroiliac Joint Dysfunction TECHNIQUE By Whitney Lowe CLINICAL EXPLORATIONS of the population have completely fused SI joints. 1 Stability at the SI joint is not only dependent on the contour surface between the adjacent bones but is enhanced by a complex webbing of supporting and surrounding ligaments and other connective tissues. On the front side of the sacrum is the expanse of the anterior sacroiliac ligament complex (Image 1). There is a similar group of ligaments, the posterior sacroiliac ligaments, on the back side of the sacrum (Image 2). Additional sacral stability is provided by the sacrotuberous ligament (Image 3). It spans between the sacrum and the ischial tuberosity. There are fi brous expansions from the biceps femoris that go directly into the sacrotuberous ligament. These connections are important because tension throughout the hamstring muscle group can be transmitted to the sacrum through the sacrotuberous ligament. That connection provides a direct relationship of lower extremity mechanics to sacroiliac joint stability. The sacrospinous ligament, which connects the sacrum with the ischial spine, is another stabilizing force across the joint (Image 3). The iliolumbar ligament also contributes to stability at the SI joint (Image 3). This ligament spans between the transverse process of L5 (sometimes L4) and the posterior iliac crest. Some sources refer to the iliolumbar as the lumbosacral ligament. 2 One of the more interesting facets contributing to stability of the sacroiliac joint has only come to light in recent Anterior sacroiliac ligaments Anterior sacroiliac ligaments. Images courtesy of Complete Anatomy. 1 KEY POINTS • Increased understanding of the biomechanics of the SI joint have led to a reevaluation of traditional approaches to treating SI joint dysfunction. • Massage has limited direct impact on the alignment of the SI joint; however, massage techniques applied to the lumbar, gluteal, and lower extremity regions can help reduce symptoms, resolve dysfunctional mechanics, and contribute to improved functioning for our clients.