What is sacroiliac joint dysfunction? Dysfunction in the sacroiliac joint is thought to cause low back and/or leg pain. The pain can be similar to pain caused by a lumbar disc herniation. This condition is generally more common in young and middle age women. The anatomical source of sacroiliac joint pain The sacroiliac joint lies next to the spine and connects the sacrum (the triangular bone at the bottom of the spine) with the pelvis (iliac crest). The joint: Is small and very strong Transmits all the forces of the upper body to the pelvis (hips) and legs Acts as a shock-absorbing structure Does not have much motion While it is not clear how the pain is caused, it is thought that an alteration in the normal joint motion may be the culprit that causes sacroiliac joint pain. This source of pain can be caused by either: Too much movement — hypermobility or instability, or Too little movement — hypomobility or fixation. The pain is typically felt on one side of the low back or buttocks, and can radiate down the leg. The pain usually remains above the knee, but at times pain can extend to the ankle or foot. Background on sacroiliac joint dysfunction For decades, the sacroiliac joint was suspected to be a cause of low back and leg pain -though difficulty in proving it with standard diagnostic tests left many in the medical profession skeptical. Also, over the last twenty to thirty years, the medical profession has focused more on discogenic pain (such as a disc herniation). In fact, to this day sacroiliac joint dysfunction remains difficult to diagnose as no non-invasive diagnostic test has been found to be able to isolate the sacroiliac joint (short of anesthetic injection blocks specifically applied to the joint).