Past research has reported that the common causes of ankle arthritis include trauma, congenital deformity, and degeneration. Among them, fracture-induced post-traumatic arthritis is most common. For patients with ankle fractures, an anatomical reduction is performed through surgical treatment. However, insufficient reduction or malunion of the fracture site may change the alignment of the ankle joint, resulting in valgus or varus deformities. Currently, most operative options for valgus arthritis aim to either restore joint alignment and/or reduce the uneven load on the cartilage. In this report, we would like to share our clinical experience of a patient with posttraumatic valgus ankle arthritis caused by severely comminuted fracture and dislocation. A satisfactory outcome could be obtained with combined fibular lengthening osteotomy and medial displacement calcaneal osteotomy.