Background Unstable ankle fractures are very frequent. Given the instability, they often require surgical treatment, but literature scarcely reports on the outcomes of their management. Questions/purposes For this systematic review we asked: (1) What are the outcomes in treatment of unstable ankle fractures? (2) What about complications of treatment in unstable fractures? (3) What factors influence the outcomes? (4) What about the role of the posterior malleolus? Methods The electronic databases PubMed, Scopus, and Embase were interrogated using the search terms “bimalleolar” or “trimalleolar” and “fracture”. Studies were included if they reported on: (1) bimalleolar or trimalleolar fracture in adults; (2) treatment; (3) outcomes reported by scales; (4) follow-up. The final review included 33 studies. The quality of the studies was evaluated with the Methodological Index for Non-randomized Studies (MINORS) questionnaire. Results All the outcomes of the thirty-three selected studies were analyzed. Discussion Surgical fixation of unstable ankle fractures should always be performed within the first 48 hours from the trauma, preventing instability and post-traumatic osteoarthritis. Surgeon should consider factor may influence functional outcomes. Posterior malleolar fractures should be fixed regardless the size, considering some individual factors.