Pain related to the sacroiliac joint can cause an intense and localized pain in the buttock, leg, hip, groin and/or abdomen. The sacroiliac joint is a large joint in the lower back. Irritation or inflammation in the sacroiliac joint can cause chronic pain. An injection of steroid, such as cortisone, will reduce inflammation and irritation, alleviating the pain. Initially, this injection can be used to diagnose if the pain is being caused by irritation of the sacroiliac joint, should the pain not be relieved immediately by the injection.