Differential points of widening and pseudo-widening of sacroiliac joint: Feature of image.

One patient, a 16-year-old male with a history of ankylosing spondylitis diagnosed 2 years ago, presented with a pelvic and both knee pain. Blood tests revealed HLA-B27 positivity. (A) (B) A plain radiograph and computed tomography (CT) scan of the sacroiliac joint showed severe bony erosions, subchondral sclerosis and joint space pseudo-widening of bilateral sacroiliac joints without ankylosis, which is compatible with New York criteria grade III. This article is protected by copyright. All rights reserved.