Although hip replacement surgery is a successful way of dealing with the pain and immobility caused by hip arthritis, 10% of the hip replacements carried out in the UK fail within 10 years. The main reason for this is the development periprosthetic osteolysis, that is, loss of bone around the site of the hip replacement. The osteolysis is thought to be due to the small particles of debris worn from the surfaces of the hip implant. These particles cause a reaction in the blood cells around the joint which in turn affects bone cells and leads to a loss of bone around the implant. The joint implant will then eventually become loose and unstable, a condition known as aseptic loosening. At present the only way to treat aseptic loosening is to have another operation to secure the hip joint, known as revision surgery. Revision surgery is not always successful and exposes the patient to the risk of major surgery. In this study we explore the potential for giving a medication (denosumab) that may prevent the loss of bone around the hip replacement implant. We will recruit patients who have been listed for revision surgery. One group of patients will be given a single dose of denosumab; another group will be given a placebo (dummy drug). At the time of the revision surgery a small sample of the bone from around the hip replacement will be taken and examined under the microscope. Comparisons will be made between the patients having the denosumab and those having placebo to find out whether the denosumab is having a beneficial effect on the bone surfaces. If successful, this study will lead to further studies to develop the use of denosumab to prevent aseptic loosening.