1. Coxa Hospital for Joint Replacement, and Faculty of Medicine and Health Technologies, University of Tampere, Tampere, Finland;
2. Finnish Arthroplasty Register, National Institute for Health and Welfare, Helsinki, Finland;
3. Department of Orthopaedics and Traumatology, Turku University Hospital, Turku, Finland;
4. The Swedish Knee Arthroplasty Register, Department of Orthopedics, Skane University Hospital, Lund, Sweden;;
5. Department of Clinical Sciences, Orthopedics, Lund University, Sweden
6. The Norwegian Arthroplasty Register, Department of Orthopaedic Surgery, Haukeland University Hospital, Bergen, Norway;
7. Department of Clinical Medicine, University of Bergen, Haukeland University Hospital, Bergen, Norway;
8. Department of Clinical Epidemiology, Aarhus University Hospital. Denmark and Danish Knee Arthroplasty Registry;
9. Department of Orthopaedic Surgery, Naestved Hospital, Denmark;