1. School of Medicine, Mayo Clinic Alix School of Medicine, Rochester, MN, USA
2. Oslo Sports Trauma Research Center, Norwegian School of Sport Sciences, Oslo, Norway
3. School of Medicine, University of California, San Francisco, San Francisco, CA, USA
4. Department of Orthopedic Surgery, University of California, San Francisco, San Francisco, CA USA
5. Department of Orthopaedic Surgery, University of California, Irvine, CA, USA