This study aims to determine the mean posterior condylar angle (PCA) in the included population and its relation to coronal alignment; and to know the clinical importance of the use of preoperative computed tomography (CT) scan in total knee arthroplasty (TKA). We randomized 50 patients with primary knee osteoarthritis into 2 groups. We used CT scan axial images to measure the PCA. In the first group we followed the CT scan plan (group 1), but in the second we did not follow the plan and adjusted rotation to the standard three degrees (group 2). The mean age of the included patients was 63 years. The radiological data of the included patients showed 5 patients with valgus deformity and 45 patients with varus deformity with the mean coronal alignment of 7.5 degrees. CT scan showed the mean PCA of 3.7 degrees (1.3 degrees). The axial knee postoperative X-ray showed the mean patellar tilt angle of 2.1 degrees (0.5 degrees) and 1.9 degrees (0.5 degrees) in groups 1 and 2, respectively. The congruence angle was 4 degrees (2.6 degrees) in group 1 and 5.5 degrees (3.2 degrees) in group 2. The median Knee Society functional score in group 1 was 85 (12), while it was 84 (7.5) in group 2. The median postoperative Western Ontario and McMaster Universities Arthritis Index score in group 1 was 84 (18.6) whereas 80.2 (13.6) in group 2. The median postoperative Bartlett score in group 1 was 30 (5), while it was 30 (6) in group 2. The use of preoperative CT scan did not improve the patient functional scores after TKA.