Temporomandibular joint (TMJ) arthritis is known to alter the mandibular development in children diagnosed with juvenile idiopathic arthritis. In a number of cases a genuine breakdown of cartilage and bone is seen in the affected joint which leads to asymmetric mandibular growth in the affected side. In cases of unilateral TMJ involvements severe mandibular asymmetric mandibular growth deviations are seen. We hypothesize that these growth deviations can be minimized and controlled by the use functional orthodontic appliance therapy.