Ultrasound-Guided Sacroiliac Joint Injection

The sacroiliac joint (SIJ) is a true diarthrodial joint with the articular surfaces of the sacrum and ilium separated by a joint space enclosed in a fibrous capsule [1]. It bears the characteristics of a synovial joint, especially in the superoanterior and inferior aspects. The superoposterior joint surface lacks a joint capsule and contains the interosseous ligament. The anterior joint capsule gives origin to the anterior sacroiliac ligament. The posterior aspect also contains the posterior sacroiliac, sacrotuberous, and sacrospinous ligaments that stabilize the joint. With increasing age, degenerative changes occur with narrowing of the synovial cleft inferiorly and subsequent fibrous ankylosis [2, 3].