Hip replacements are being performed on an increasingly active population, who are likely to wear their implants out prematurely. New hip replacements have been devised to minimise the risk of failure. DePuy RSA RCT is a randomised controlled trial designed to compare the performance of two established types of hip replacements using Corail and Tri-Lock stems along with Deltamotion acetabular component. The primary objective of the trial is to compare the long term stability of these two devices.To do this, the study will use an advanced 3D Xray technique to detect migration of the components at 3 years. The study will also measure micromotion of Corail, Tri-Lock and Deltamotion components, patient reported outcome measures and change in bone density.This study is being conducted at a single site, at the Nuffield Orthopaedic Centre, Oxford.