Aim: The study intended to determine the specific ultrasonographic features of acute arthritis with periarticular bone erosions caused by acute osteomyelitis (OM), rheumatoid arthritis (RA) and gouty arthritis (GA). Method: We included 33 patients (seven with acute OM, 18 with RA flares, and eight with GA attacks) having acute monoarthritis or oligoarthritis, and receiving ultrasound (US) examinations in the acute stage. The US images were rated by three rheumatologists blinded to the diagnosis. The median scores of their evaluation of the subcutaneous tissue, periosteum, and synovium were compared. Interrater reliability was calculated using Cronbach's alpha. Results: The highest mean grade of subcutaneous edema appeared in patients with acute OM, and grade 2 edema was more frequent than patients with RA and GA (P =.003 and P =.026, respectively; α =.869). The prevalence of subcutaneous power Doppler signal was also higher in patients with acute OM than in those with RA and GA (P <.001 and P =.041, respectively; α =.756). Periosteal vascularity presented more frequently in acute OM (P =.003 compared with RA; P =.041 compared with GA), but the interrater reliability was poor (α =.518). The tophaceous material in GA was distinctive from OM and RA (P =.010 and P <.001, respectively; α =.774). Conclusion: The most discriminative US features in this study were the subcutaneous tissue changes in addition to the periosteal findings. US could contribute to the differential diagnosis of acute erosive arthritis.
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