1. Cabrini Institute and Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University; Monash Department of Clinical Epidemiology; Melbourne VIC Australia 3144
2. Vanderbilt University School of Medicine; Departments of Physical Medicine and Rehabilitation, and Orthopaedics; 2201 Children's Way, Suite 1318, Nashville Tennessee USA 37202
3. University of Oulu; Division of Orthopaedic and Trauma Surgery, Department of Surgery, Oulu University Hospital, Medical Research Center; Oulu Finland
4. Monash University; Monash Department of Clinical Epidemiology, Cabrini Institute and Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine; Melbourne Australia