1 MRC/Arthritis Research UK Centre for Musculoskeletal Ageing (CIMA), Institute of Cellular Medicine and Newcastle University Institute for Ageing, Newcastle University, Newcastle Upon Tyne, UK. carole.proctor@ncl.ac.uk.
2 MRC/Arthritis Research UK Centre for Musculoskeletal Ageing (CIMA), Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, UK.