Describe the abnormality
Bilateral sacroiliac joint space narrowing, subchondral erosions, subchondral sclerosis, and subchondral fatty marrow infiltration.
What is the differential diagnosis?
Inflammatory bowel disease.
Reactive arthritis (Reiter syndrome)
What is the most likely diagnosis?
What are the markers of active inflammation?
Erosions with high signal intensity on STIR or T2- weighted images, subchondral edema, and enhancement within or adjacent to the sacroiliac joint.
What are the markers of chronic disease?
Low signal intensity on T1- and T2- weighted images, subchondral sclerosis, narrowing of the joint spaces, bone bridging, and ankylosis.