1. Children’s Hospital, Pediatric Research Center, University of Helsinki, Helsinki University Hospital, Helsinki, Finland
2. Orton Orthopaedic Hospital, Orton, Helsinki, Finland
3. Research Institute Orton, Orton, Helsinki, Finland
4. Department of Medicine, Division of Rheumatology, Helsinki University Hospital and University of Helsinki, Helsinki, Finland
5. Department of General Practice and Primary Health Care, University of Helsinki and Helsinki University Hospital, Helsinki, Finland