What Is the SI Joint?
Short for sacroiliac joint. There are two of them in your lower back, and they sit on each side of your spine. Their main job is to carry the weight of your upper body when you stand or walk and shift that load to your legs
Sacroiliac (SI) joint pain is felt in the low back and buttocks. The pain is caused by damage or injury to the joint between the spine and hip. Sacroiliac pain can mimic other conditions, such as a herniated disc or hip problem. Accurate diagnosis is important to determine the source of pain.