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Imaging features of major arthritides
• OA: plain films: asym joint space narrowing (JSN), osteophytes, subchondral sclerosis & cysts; subchondral “gull-wing” erosions may be seen in less-common erosive OA; MRI may show early disease not seen on plain films; U/S ≈ MRI for structural damage ⊖ • RA: plain films: symmetric JSN, early = periarticular osteopenia; late = marginal erosions; subluxations; MRI & U/S can detect early and subclinical disease; MRI ≈ U/S for erosions • Gout: plain films: early = nonspec swelling; late = tophus, joint erosions w/ overhanging edges; U/S for detection of microtophi (double-contour sign); dual-energy CT (DECT): identify articular/periarticular UrA deposits vs. calcium deposits; MRI ≈ U/S for erosions • Spondyloarthritis: e/o sacroiliitis: plain films: early = pseudo-widening SI joint space, late = sclerosis, erosions, ankylosis; SI MRI ↑ Se for early Δ; U/S ≈ MRI to detect enthesitis