Mutations resulting in hip dysplasia represent rare but important causes of hip osteoarthritis (OA). Commoner forms of genetic variation, with more subtle effects hip shape, may also contribute to hip OA. However, though several components of hip shape are associated with hip OA, rather than a causal role, these relationships may reflect altered hip modeling secondary to OA. The present proposal is intended to identify the major common genetic determinants of hip shape, thereby enabling (i) Mendelian Randomisation studies to examine causal pathways between hip shape and OA, and, in the case of shape parameters found to play a causal role, (ii) the identification of novel genetic risk factors for OA acting through specific alterations in hip shape. Exposure Variables: GWAS data imputed to latest version of Hapmap. Further analyses may be performed in relation to rare variants from exome sequence data in those participants involved in UK10K, and to methylation data in those included in ARIES.