Almost all children with childhood arthritis experience inflammation of the jaw during the course of their disease. To assess the jaw, detailed imaging (MRI) is needed. The jaw is a complex joint, consisting of different parts which together lead to a seamless opening and closing movement. One part is the disk, a structure that moves along the bone while opening and closing the mouth. If the disk is not in the correct position, the patient can feel or hear a click when opening or closing the mouth. It is unclear how often the disk is not in the correct position in patients with jaw arthritis and if this incorrect position leads to signs of inflammation on the MRI. In this study, we will use artificial intelligence to determine the disk position on MRI and will try to relate these findings to treatment response.