This study stared in 2004. The Twin Research Unit has the largest and most extensive collection of musculoskeletal disease phenotypes and genotypes of twin subjects in the world. Previous analyses of our existing data have given us important insights into genetic and environmental influences across the spectrum of musculoskeletal disease. This study aims to realise the full potential of the data. It will allow us to preserve the existing dataset, make it more widely accessible, provide a central repository for future twin studies of musculoskeletal diseases, and act as a focal point for planning longitudinal studies.