The sacroiliac or SI joint is a joint within the pelvis that is frequently injured in falls and motor vehicle accidents. When an individual falls and lands on their buttocks (either square on, or to one side) the sacroiliac joint can sustain damage. Specifically the ligaments and tendinous structures overlying and supporting the SI joint become damaged. In a motor vehicle accident when the injured person’s foot is placed forcibly on the floor at the time of impact, it transmits forces up the leg into the pelvic region and sacroiliac joint; hence the common association of SI joint injury and motor vehicle accidents. Treatment of the sacroiliac joint requires specific image guided injections. There are two choices for injection of the sacroiliac joint, one involves the placement of a needle into the joint and the other involves mapping of the nerves that innervate the joint. Both of these are effective approaches and can provide sustained benefit. When sustained benefit is not obtained, longer lasting procedures such as radiofrequency denervation can be considered (please see radiofrequency denervation for further information of this procedure). It is important to note that sacroiliac problems frequently occur in combination with facet problems; when these two conditions are present simultaneously it is referred to as a posterior joint syndrome. Incomplete relief will occur if both structures are not treated. Both facet and sacroiliac joint problems also frequently follow surgical intervention in the lumbar region.