Multidirectional distal femoral malunion and limb shortening lead to functional deficit and decreased quality of life. A corrective osteotomy might be necessary to cope with these issues. The inception of computer-assisted planification and the introduction of patient-specific instrumentation based on 3D printing technology with personalized osteotomy guides provide high correction accuracy, effectiveness, time-saving, and reduce potential complications. The present study describes a case of correction osteotomy using this procedure in a young patient with multidirectional malunion who recovered from a painful joint with functional limitations at a two-year follow-up.