This study is looking at the influence of your genes on the development of Osteoarthritis in the knee and how these factors can be related to being overweight. We are looking at a group of identical and non-identical twins with regards to their development of osteoarthritis in the knee. Using twins allows us to explore whether being overweight affects the way their knees are knock-kneed or bow legged and also whether genetic factors are important in the shape and position of the knees. Over the last 24 months we have successfully recruited 308 sets of identical and non-identical twins who had X-rays of their legs done. These x-rays are taken of the whole lower limb, from this film we take standard measures to determine how twins knees have become malaligned. These x-rays are currently being analysed after training with the leading alignment expert in the United States. We will also look at their knee X-rays and compare them with previous ones taken 10 years before in order to see if their osteoarthritis has become progressive and how, or if, weight has influenced the straightness of their legs, and if their knock knees or bow legs has influenced their worsening arthritis. This malalignment in knees is important in the future of osteoarthritis as it is something that can be modified and early intervention may reduce the burden of progressive osteoarthritis. The data have now all been collected and analysis, interpretation and writing up of the results is ongoing.