Sacroiliitis is one potential cause of SI joint dysfunction. Your sacroiliac (SI) joints are where your spine (sacrum) and pelvis (iliac) connect. Your sacrum is the triangle-shaped bone at the ...

Your SI joint, or sacroiliac joint, connects your sacrum (otherwise known as the tailbone) and your illiac, the bone of the topside of your pelvis. Technically, there's two of these joints—one on ...