1. School of Medicine, Keele University , Keele, Newcastle, ST5 5BG , UK
2. Department of Orthopaedic Surgery, Duke University School of Medicine , Durham, North Carolina , USA
3. Department of Population Health Sciences, Duke University School of Medicine , Durham, North Carolina , USA
4. Duke Clinical Research Institute, Duke University , Durham, North Carolina , USA
5. Department of Physical Therapy, University of Florida , Gainesville, Florida , USA
6. Brooks Rehabilitation , Jacksonville, Florida , USA
7. Department of Psychiatry, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania , USA
8. Department of Physical Therapy, University of Pittsburgh School of Health and Rehabilitation Sciences Pittsburgh , Pittsburgh, Pennsylvania , USA