Bilateral symmetrical Sacroilitis is hallmark of :
Ankylosing spondylitis
Juvenile Rheumatoid ahritis
Nail Patella syndrome
Osteitis condensans ilii
Diagnostic radiological features of Ankylosing spondylitis are: Bilateral symmetrical Sacroilitis (earliest and most specific feature) Bamboo-spine (knobby spine, poker back or universal syndesmophytosis) is a characteristic feature of it. Syndesmophytes - ossifications of the outer fibers of annulus fibrosis. Enthesitis (earliest pathological change) Uncommon involvement of small joints of hand and feet.
Musculoskeletal Radiology