Development of synovial and serum biomarkers allows families to have more complete information regarding prognosis, allowing for informed decisions regarding treatment. Addressing juvenile idiopathic arthritis (JIA) as early as possible to prevent joint damage will significantly improve the long-term outcome and life enjoyment of children with arthritis. This project focuses on prediction of extension in JIA. Since disease progression increases the risk for disability, early prediction of this course is essential; unfortunately, no reliable clinical or laboratory predictors have been established. Within this proposal, Dr. Brescia will validate the candidate synovial biomarkers that she has developed to predict disease progression from persistent to extended oligoarticular JIA on a larger, independent cohort of well-characterized existing samples from collaborating institutions within the CARRA network. Additionally, she will study how cells which line the joint contribute to progression of disease.