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