1 Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford OX3 7LD, UK; Oxford Biomedical Research Centre, Leeds, UK. Electronic address: laura.coates@ndorms.ox.ac.uk.
2 Academic Unit of Health Economics, Leeds Institute of Health Sciences, University of Leeds, Leeds, UK.
3 Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, UK.