In patients with juvenile idiopathic arthritis (JIA) growth impairment and variance in body composition are well-known long-term complications. In the active phases of the disease, particular patients with systemic and polyarticular JIA reveal growth impairment. Some experience “catch-up” growth following reduction in disease activity and lower glucocorticoid doses. Although new therapeutic options are available, there are still 10–20 % of patients with severe forms of the disease who show continuous growth disturbance. Only few studies have specifically addressed body composition in JIA. Bone mass deficits in part could be related to the deficits of muscle mass. Study data on growth hormone treatment in short children with JIA are promising in respect of growth development, final height and body composition. The major goal for physicians is optimal disease control while maintaining normal growth and body composition. Early recognition of patients who develop prolonged growth and body composition disturbances is important as these abnormalities contribute to long-term morbidity and need to be addressed both diagnostically and therapeutically.