Ankylosing Spondylitis – Sacroiliitis

Earliest sign of AS is indistinctness of the sacroiliac joint. Subchondral bony erosions, subchondral sclerosis, and bony proliferation may eventually lead to bony fusion. In the later stage, the sacroiliac joint may not be visible or may present only as a thin dense line. Bamboo spine, also prominent here, is an AS feature caused by syndesmophytes formation.