1. Faculty of Medicine, Department of Clinical Sciences Lund, Orthopaedics, Clinical Epidemiology UnitLund UniversityLund Sweden
2. Faculty of Medicine, Department of Clinical Sciences Lund, Rheumatology and Molecular Skeletal BiologyLund UniversityLund Sweden
3. Department of OrthopaedicsSkåne University HospitalLund Sweden
4. Clinical Epidemiology Research and Training UnitBoston University School of MedicineBoston Massachusetts