[1] Univ Bristol, Dept Social Med, Bristol BS8 2PR, Avon, England
[2] Kings Coll Hosp Dulwich, Rheumatol Outcomes Res Unit, London, England
[3] Univ E Anglia, Sch Hlth Policy & Practice, Norwich NR4 7TJ, Norfolk, England
[4] Southmead Hosp, Dept Orthopaed Surg, Bristol, Avon, England
[5] Frenchay Hosp, Dept Orthopaed Surg, Bristol BS16 1LE, Avon, England
[6] Somerset Hlth Author, Taunton, Somerset, England