The goal of this clinical trial is to compare three different maintenance and step-down treatment strategies in children and adolescents with juvenile idiopathic arthritis in sustained remission. The main questions it aims to answer are: * Is the proportion of study participants with a disease flare different between each of the two drug withdrawal arms and the stable treatment arm during 12 months? * Does the proportion of study participants with a disease flare differ between the two drug withdrawal arms during 12 months? * How long time does it take before a disease flare occurs, and how long does it take before disease remission is reestablished for participants in the different treatment arms? Participants will be randomized to either A) continued stable treatment with methotrexate and tumor-necrosis alpha inhibitor (TNFi); B) gradual withdrawal of methotrexate while continued stable dose TNFi; or C) gradual withdrawal of TNFi. Participants will be examined every 4 month, and with extra visits if they experience increased symptoms or suspect a disease flare. If a flare occurs, the medications received at study inclusion will be restarted.