1. Department of Public Health, Section of Sport Science, Aarhus University, Aarhus, Denmark.
2. Orthopaedic Surgery Research Unit, Science and Innovation Center, Aalborg University Hospital, Aalborg, Denmark.
3. Center for Sports Medicine, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
4. Department of Public Health, Section of Biostatistics, Aarhus University, Aarhus, Denmark.
5. Department of Public Health, Section for Epidemiology, Aarhus University, Aarhus, Denmark.
6. Department of Orthopaedics, Aarhus University Hospital, Aarhus, Denmark.