Dysfunction in the sacroiliac joint, also called the SI joint, can sometimes cause lower back and/or leg pain. Leg pain from sacroiliac joint dysfunction can be particularly difficult to differentiate from radiating leg pain caused by a lumbar disc herniation (sciatica) as they can feel quite similar. Sacroiliac Joint Dysfunction Video Anterior view of the pelvis highlighting the sacroiliac joints on both sides. For decades, the sacroiliac joint was suspected as a common cause of low back and/or leg pain, although difficulty in accurate diagnostic testing left many in the medical profession skeptical. Today it is estimated that the sacroiliac joint is responsible for 15% to 30% of lower back pain cases. Inflammation of the sacroiliac joint (sacroiliitis) can also produce pelvic pain