Over the last decade, total ankle replacement (ankle prosthesis) has become increasingly popular in the surgical management of end-stage ankle osteoarthritis. Clinical and radiographic outcomes of the implantation of an ankle prosthesis have been assessed, but few gait analysis studies have examined the functional performance associated with the ankle prosthesis. Moreover, no studies have directly compared the improvement in foot mechanics during gait after total ankle replacement based on the origin of the osteoarthritis. It might be expected that the two subtypes of post-traumatic ankle osteoarthritis would benefit differently from total ankle replacement in terms of foot mechanics during gait. The overall objective of this study was to compare the benefits of total ankle replacement in terms of foot mechanics of patients suffering from post-fracture ankle osteoarthritis with those of patients suffering from post-sprain ankle osteoarthritis.