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Objectives: Intra-articular corticosteroids injection (IAC) is a mainstay for the treatment of children with chronic arthritis; nonetheless its efficacy showed variability among published studies and it is still not possible to predict the outcome in a single patient. Our objective was to study the profile of biomarkers in the synovial fluid (SF) obtained at the time of injection and establish if such profile predicts duration of effect., Methods: SF obtained from patients who underwent knee arthrocentesis and injection was procured and stored for cytokine analysis. Records of those patients who had at least 6 months of follow-up from the injection were reviewed. Time to flare was recorded. Levels of IL-6, IL-1alpha, TNF-alpha, IL-2sR, MMP-3, IL-10 and TGF-Beta1 were measured by ELISA. For primary analysis each patient was utilized once. For secondary analysis each injected knee was considered a single event., Results: 60 samples from 33 patients were obtained. In the primary analysis we found a correlation between MMP-3 synovial fluid levels and outcome at 6 months (p=0,02; p=0,03 for different quartiles). In the secondary analysis we found that IL-6 and IL-10 levels predicted outcome at six and at 12 months (IL-6: p=0.01; p=0.02 respectively) (IL-10: p=0.017; p=0.01 respectively), with higher levels of IL-6 predicting shorter time to relapse and higher levels of IL-10 longer duration of corticosteroids effect., Conclusions: Our study identified MMP-3 and possibly IL-6 and IL-10 as candidates for the development of a set of biomarkers to predict response to IAC among children with chronic arthritis at the time of injection.