National Institute for Health Research Bristol Biomedical Research Centre, University Hospitals Bristol NHS Foundation Trust and University of Bristol, Bristol, UK; Musculoskeletal Research Unit, Translational Health Sciences, Bristol Medical School, University of Bristol, Learning & Research Building (Level 1), Southmead Hospital, Bristol, UK. Electronic address: skk31@cantab.net. Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland; Institute of Clinical Medicine, Department of Medicine, University of Eastern Finland, Kuopio, Finland; Central Finland Health Care District Hospital District, Department of Medicine, Jyväskylä, Finland District, Jyväskylä, Finland.