The goal of this study is to investigate how having a total ankle replacement affects balance over time. We will be examining the impact that having a total ankle replacement has on both the affected limb and the unaffected limb. When a person tries to stand still, they constantly make small changes in how their weight is distributed. With a replaced ankle joint, these changes become harder to make quickly, and patients can easily lose their balance. We will be using data that has been collected on hundreds of ankle replacement patients from before surgery though a 2 year follow-up assessment in order to understand how their balance is affected. As well as examining how these patients use other joints in order to compensate for deficiencies in mobility and proprioceptive feedback at the ankle.