In this study, a new CT measurement system was developed for preoperation evaluation of total knee replacement (TKR). To validate the developed imaging processing systems, TKR patients with and without a bowed lower limb were recruited. All patients underwent plain radiographs and CT scan before a TKR procedure. The precision and effectiveness of two measurements validated by an orthopedic surgeon and evaluated using the developed 3D computed tomography image system were compared. In vivo statistics data, particularly for Taiwanese patients, showed no difference between bowed lower limb and normal lower limb groups. The results of this study did not reveal a significant difference between the 3D-reconstructed CT images and 2D plain radiographs. However, the proposed 3D-reconstructed CT image measurement system demonstrated consistent measurements for TKR patients and for the bowed lower limb group in preoperative evaluation. The implemented system could be used in conjunction with the current 2D radiograph approach. The proposed system assist surgeons and patients when discussing operations and clinical approaches. Clinical results validated the system.