Musculoskeletal pain and its effect on daily activity and behaviour in Icelandic children and youths with juvenile idiopathic arthritis: a cross-sectional case-control study oleh Svanhildur Arna Oskarsdottir, Audur Kristjansdottir, Judith Amalia Gudmundsdottir, Solrun W. Kamban, Zinajda Alomerovic Licina, Drifa Bjork Gudmundsdottir, Bjorg Gudjonsdottir