OBJECTIVE To define the risk and incidence of post-traumatic ankle arthritis requiring ankle arthroplasty or fusion after ankle fracture in a large cohort and compare that rate to matched healthy patients from the general population. METHODS Multiple databases were used to identify patients either treated surgically or nonsurgically for ankle fractures. Each patient was matched to 4 individuals from the general population (13.5 million) with no previous treatment for ankle fracture. Ankle fusion and replacement incidence was compared using the Kaplan-Meier analysis. METHODS Incidence of arthroplasty or fusion in all patients managed for rotational ankle fractures. RESULTS We identified 44,133 and 88,266 patients who had undergone operative management of ankle fracture (OAF) or nonoperative management of ankle fracture (NOAF) by an orthopaedic surgeon, respectively. Three hundred six (0.65%) patients who had OAF eventually underwent fusion or arthroplasty after a median 2.8 and 6.9 years, respectively. Among NOAF, n = 236 (0.17%) patients underwent fusion or arthroplasty after a median of 3.2 and 5.6 years, respectively. Surgical treatment, older age, comorbidity, and postinjury infection significantly increased the risk of fusion/arthroplasty. Compared with matched controls, the risk of fusion/arthroplasty was not independent of time, following an exponential decay pattern. OAF patient risk of fusion/arthroplasty was >20 times the general population in the 3 years after injury and approached the risk of NOAF by 14 years. CONCLUSIONS Compared with a matched control group, and after adjustment for medical comorbidity, rotational ankle fractures requiring surgical open reduction internal fixation increased the likelihood of arthroplasty or fusion by 3.5 times. This study allows for accurate prognostication of patient risk of arthroplasty or fusion, using patient- and injury-specific risk factors, both immediately after the initial injury and then subsequently during the follow up. METHODS Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.