The radiographic changes include erosions and sclerosis, predominantly affecting the ilium, and widening of the articular space. Although joint space narrowing and bony ankylosis can occur, this is much less frequent than in classic ankylosing spondylitis. A prominent finding may be blurring and eburnation of apposing sacral and iliac surfaces above the true joint in the region of the interosseous ligament.
Psoriatic arthritis. Bilateral, though somewhat asymmetric, narrowing of the sacroiliac joints.