1. Health Economics Research Centre, Nuffield Department of Population Health; University of Oxford; Oxford UK
2. Oxford NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology, and Musculoskeletal Sciences; University of Oxford; Oxford UK
3. MRC Lifecourse Epidemiology Unit; University of Southampton; Southampton General Hospital Southampton UK
4. GREMPAL Research Group (Idiap Jordi Gol) and Musculoskeletal Research Unit (Fundació IMIM-Parc Salut Mar); Universitat Autònoma de Barcelona; Barcelona Spain