['The purpose of the present study was to compare the change in tibial posterior slope angle (PSA) between patients treated via computer-assisted and conventional closed-wedge high tibial osteotomy (CWHTO). It was hypothesized that a decrease in the PSA would be less in the computer-assisted group than in the conventional group.', 'Data on a total of 75 computer-assisted CWHTOs (60 patients) and 75 conventional CWHTOs (49 patients) were retrospectively compared using matched pair analysis. The pre- and postoperative mechanical axis (MA) and the PSA were radiographically evaluated. The parallel angle was defined as the angle between the joint line and the osteotomy surface. The data were compared between the two groups.', 'The postoperative radiographic MA averaged 1.3°\xa0±\xa02.6° valgus in the computer-assisted group and 0.3°\xa0±\xa03.1° varus in the conventional group. The change in PSA averaged -0.8°\xa0±\xa00.9° in the computer-assisted group and -4.0°\xa0±\xa02.2° in the conventional group. The parallel angle averaged 0.2°\xa0±\xa03.0° in the computer-assisted group and 6.2°\xa0±\xa05.3° in the conventional group.'] Does computer-assisted navigation decrease the change in the tibial posterior slope angle after closed-wedge high tibial osteotomy?