If you have pain in your lower back, buttock or pelvis, you may wonder whether your sacroiliac (“SI”) joint is involved. SI joint pain can develop for several reasons, including injury, arthritis, pregnancy-related changes and differences in how your body moves. Your SI joints connect your sacrum at the bottom of your spine to the two sides of your pelvis. These joints help transfer forces between your upper body and legs. When an SI joint becomes irritated or inflamed, you