The sacroiliac joint is a low-motion joint that connects the hip bones to either side of the sacrum, acting primarily as a shock-absorber between the lower body and torso. This joint can also be thought of as the point where the base of the spine connects to the pelvis. The sacroiliac joint is a combination of a synovial joint and the sacroiliac ligaments. Dysfunction in the sacroiliac joint (also called the SI joint) can produce significant lower back pain, as well as the pelvic, groin, and hip pain. Sacroiliac joint dysfunction can be the result of too much motion, too little motion, or inflammation of the joint.