Abnormal sacroiliac joint morphology

What it means

An anomaly of the sacroiliac joint, which connects the base of the spine (sacrum) to the ilium (a hip bone).

The sacroiliac joint (SIJ) is a true diarthrodial joint: matching articular surfaces separated by a joint space containing synovial fluid and enveloped by a fibrous capsule. It does, however, have unique characteristics not typically found in other diarthrodial joints. The SIJ has fibrocartilage in addition to hyaline cartilage. There is discontinuity of the posterior capsule. Rather than being smooth, the articular surfaces have many ridges and depressions that minimize movement and enhance stability. Primary stability, however, is attributed to the many adjacent ligaments.

Rare diseases that can present with this7

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Abnormality of the sacroiliac joint