1. Academic Primary Care, Institute of Applied Health Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen , Foresterhill, Aberdeen AB25 2ZD , UK
2. Aberdeen Centre for Arthritis and Musculoskeletal Health (Epidemiology Group), School of Medicine, Medical Sciences and Nutrition, University of Aberdeen , Foresterhill, Aberdeen AB25 2ZD , UK
3. Health Economics Research Unit, Institute of Applied Health Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen , Foresterhill, Aberdeen AB25 2ZD , UK
4. Aberdeen Business School, Robert Gordon University , Aberdeen, AB10 7QE , UK
5. Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford , Oxford OX3 7LD , UK
6. School of Health Sciences, University of East Anglia , Norwich, NR4 7TJ , UK