[1] Keele Univ, Arthrit Res Campaign Natl Primary Care Ctr, Keele ST5 5BG, Staffs, England
[2] Oslo Univ Hosp, Div Neurosci & Musculoskeletal Med, FORMI Commun Unit Musculoskeletal Disorders, Oslo, Norway
[3] Diakonhjemmet Hosp, Natl Resource Ctr Rehabil Rheumatol, Oslo, Norway