J Rheumatol
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Core outcome set (COS) is the minimum set of outcome domains that should be measured and reported in clinical trials. We analyzed outcome domains, prevalence of use of COS published by Outcome Measures in Rheumatology (OMERACT) initiative, outcome measures for outcome domains recommended by OMERACT COS, duration and size of randomized controlled trials (RCT) testing nonsurgical interventions for osteoarthritis (OA). ⋯ Suboptimal use of recommended COS and heterogeneity of outcome measures is reducing quality and comparability of OA trials and hinders conclusions about efficacy and comparative efficacy of nonsurgical interventions. Interventions for improving study design of trials in this field would be beneficial.