BACKGROUND: Deformation of the talus and the distal tibia can be frequently observed during ankle joint osteoarthritis (OA). The aim of this study was to objectify these morphologic changes. We hypothesized that a flattening of the talus and a broadening of the distal tibia surface occurs in end-stage OA of the ankle joint. METHODS: Twenty-seven computed tomography (CT) ankle joint examinations of unilateral ankle OA were matched by sex and age with 27 CT examinations of healthy ankle joints. Three-dimensional reformatting and measurements were performed with geometry analysis software. The following parameters were assessed: sagittal radius of the talus, talus height, and mediolateral and anteroposterior width of the distal tibial joint surface. RESULTS: Medial, midsagittal, and lateral sagittal arc radii of osteoarthritic tali were significantly larger compared to tali of controls. There was a statistically significant difference in the height of the osteoarthritic talar dome in the medial and in the lateral frontal segment and in the medial central segment compared to tali of controls. The anteroposterior width and the sagittal curvature of the distal tibia was significantly larger in OA ankles than in the control group. The mediolateral measurements were comparable across both groups. CONCLUSION: Flattening of the talus appears to be more pronounced in the frontal aspect of the talus. The distal tibia broadens anteroposteriorly. These findings may contribute to better understanding of ankle OA development. LEVEL OF EVIDENCE: Level III, retrospective comparative cohort study.