1. Division of Orthopaedic Surgery, Section of Rehabilitation, Oslo University Hospital, Oslo, Norway;
2. Division of Orthopaedic Surgery, Oslo University Hospital, Oslo, Norway;
3. Institute of Clinical Medicine, University of Oslo, Oslo, Norway;
4. Division of Orthopaedic Surgery, Section of Research, Oslo University Hospital, Oslo, Norway;
5. Institute of Health and Society, Faculty of Medicine, University of Oslo, Oslo, Norway