High tibial osteotomy is a realignment procedure to transfer weight-bearing load to the intact compartment of the knee to alleviate symptoms, slow disease progression, and defer subsequent total knee arthroplasty. To prevent overcorrection or undercorrection, it is not only important to have an exact preoperative calculation of the desired correction angle, but it is also critical to have an accurate intraoperative technique. 85 consecutive patients (90 knees) were enrolled, who were available at 1-year follow-up after a medial opening wedge high tibial osteotomy using a kinematic navigation system or a conventional method, for medial unicompartmental osteoarthritis. On radiographic assessment, the navigation group showed better results than the conventional group in both the mechanical axis and the coordinate of the weight-bearing line on a full-length standing anteroposterior radiograph (3.9 degrees +/- 1.0 degrees vs. 2.7 degrees +/- 2.2 degrees of valgus, P < 0.01), (62.3 +/- 2.9% vs. 58.7 +/- 6.6% coordinate at the tibial plateau, P < 0.01). There was no significant difference in the alteration of tibial slope between the two groups. On clinical assessment, the navigation group showed better results in both the mean Hospital for Special Surgery knee score (84 +/- 8 vs. 79 +/- 7, P < 0.01) and the mean Lysholm knee score (85 +/- 6 vs. 83 +/- 5, P < 0.05). There was no significant difference in operation times between the two groups. Kinematic navigation-guided high tibial osteotomy is a reproducible and reliable procedure compared to conventional high tibial osteotomy.