1 Centre for Epidemiology Versus Arthritis, Centre for Musculoskeletal Research, Division of Musculoskeletal and Dermatological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK. janet.mcdonagh@manchester.ac.uk.
2 National Institute for Health Research Biomedical Research Centre, Manchester University Hospital NHS Trust, Manchester, UK. janet.mcdonagh@manchester.ac.uk.
3 School of Health Sciences, University of Dundee, Dundee, UK.