Malunion of the ankle and hindfoot after fractures of the ankle, talus and calcaneus is not uncommon and can lead to significant sequelae such as deformity, pain and severe disability. Malunion predominantly affects articular congruency and anatomical axis of the joints leading to eccentric loading, altered peak stresses on the articular surfaces and impingement pain. If left alone, this abnormal loading of the joint surfaces will lead to the progressive development of posttraumatic osteoarthritis. The majority of these malunion cases are caused by missed, neglected or underestimated fractures and ligamentous injuries, inadequate reduction and/or fixation of fracture dislocations, and secondary displacement due to inadequate after treatment. Patient-related factors include noncompliance, poor bone quality, systemic diseases like diabetes and rheumatoid arthritis, vascular disease and other conditions that may lead to impaired healing. Besides solid malunions, non-unions, aseptic and septic necrosis may be observed. This chapter reviews the assessment and treatment of posttraumatic ankle and hindfoot deformities.