Gemini MK II implants (Link, Germany) were used. VectorVisionâ CT-free navigation system (BrainLab, Germany) was employed for the TKA. For each subject, computer-navigation TKA and the conventional TKA were separately performed on two knee joints. The operative method and order of the operations were decided on a randomized basis. All the patients and doctors conducting follow-up study and performing imaging measurement were blind to selection of the operation. Student t test was used for statistical analysis.