There are many different terms for sacroiliac joint problems, including SI joint dysfunction, SI joint syndrome, SI joint strain, and SI joint inflammation. Each of these terms refers to a condition that causes pain in the SI joints from a variety of causes. As with most other joints in the body, the SI joints have a cartilage layer covering the bone. The cartilage allows for some movement and acts as a shock absorber between the bones. When this cartilage is damaged or worn away, the bones begin to rub on each other, and degenerative arthritis (osteoarthritis) occurs. This is the most common cause of SI joint dysfunction. Degenerative arthritis occurs commonly in the SI joints, just like other weight-bearing joints of the body.