The Norwegian JIA Study (NorJIA) is a prospective, longitudinal, multicenter, observational study of 250 children with juvenile idiopathic arthritis (JIA) and 250 healthy controls, attending the three Norwegian university clinics in Bergen, Tromsø, or Trondheim. The study will run over 5 years, and include extensive clinical, laboratory, radiological and oral examinations at baseline and after 2 years follow-up. There will be a special focus on the jaw (temporomandibular joints) with extensive imaging and clinical examination, aiming at establishing scoring systems for active and chronic disease and growth disturbances. Another focus is to study mouth and teeth problems, such as caries and gingivitis, and look for predictors of poor oral health in children with JIA compared to health peers. As chronic inflammation, reduced physical activity and certain anti-inflammatory drugs can be detrimental for bone strength and development, the investigators also want to study the bone health of children with JIA, and look for predictors of poor bone mineral density. The results of the study may contribute to better diagnostics of inflammatory processes, earlier detection of poor oral or bone health, and thereby point to possible prevention strategies to increase quality of life for children with JIA in the future.

Inclusion Criteria:

• fulfilling the ILAR criteria for juvenile idiopathic arthritis

Exclusion Criteria:

• no consent

Patients with juvenile idiopathic arthritis followed at any of the three participating centers according to hospital files. Controls are recruited at The Oral Health Centre of Expertise (Tk) Mid-Norway (TkMN), TkWest or at Tk Northern Norway (TkNN) from their lists of children due for a free visit to the dentist according to the Norwegian public dental service policy.