Morphology of the Sacroiliac Joint

The sacroiliac joints form parts of two of three joints of the pelvic girdle. Located posteriorly, the joints are formed by the articulation of the iliac part of the innominate (coxal) bone with the corresponding side of the sacrum. Embryologically, the anterior sacroiliac joint portion develops in the same way as other diarthrodial joints starting around the eighth week of gestation. Sexual dimorphism is well recognized, as appearing in both the anterior articular and posterior inter-osseous parts of the sacroiliac joint having been shown that females have a larger joint than males. The subchondral bone lamellae below both the sacral and iliac auricular surfaces at the anterior sacroiliac joint region present high-density regions. In contrast, the posterior syndesmotic area is characterized to be discontinuous. Here, the bone lamellae are disrupted by ridges and groves, forming insertional points of the interosseous and posterior ligamentous apparatus.