1. Department of Physical Therapy, University of Alberta, Edmonton, Alberta, Canada
2. Clinical Epidemiology Program, Ottawa Hospital Research Institute, 725 Parkdale Avenue, Ottawa, Ontario K1Y 4E9, Canada
3. Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
4. Division of Orthopaedic Surgery, Department of Surgery, The Ottawa Hospital, 1053 Carling Avenue, Ottawa, Ontario K1Y 4E9, Canada
5. Department of Statistics and Biostatistics, Rutgers University, The State University of New Jersey, 473 Hill Center, Busch Campus Rutgers University 110 Frelinghuysen Road Piscataway, NJ 08854-8019, USA
6. Division of General Internal Medicine, Rutgers Robert Wood Johnson Medical School, Rutgers Biomedical and Health Sciences, Rutgers, The State University of New Jersey, 125 Paterson St, New Brunswick, NJ 08901, USA
7. Division of General Internal Medicine, Cumming School of Medicine, University of Calgary, FMC North Tower, 1403 29th Street NW, Calgary, Alberta T2N 2T9, Canada
8. Department of Epidemiology and Public Health, University of Maryland School of Medicine, Suite 200, Howard Hall, 660 West Redwood Street, Baltimore, MD 21201, USA