1 Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD, United Kingdom. Electronic address: raashid.luqmani@ndorms.ox.ac.uk.
2 Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, CB2 2QQ, United Kingdom. Electronic address: dj106@cam.ac.uk.