<prompt> Bilateral symmetrical Sacroilitis is hallmark of :Ankylosing spondylitisJuvenile Rheumatoid ahritisNail Patella syndromeOsteitis condensans ilii  <response>: 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. 