Abstract:[Objective] To introduce the surgical technique and preliminary clinical results of medial opening wedge high tibial osteoto- my (MOWHTO) under OrthoPilot navigation for medial knee osteoarthritis. [Methods] From August 2018 to February 2021, 34 patients (44 knees) with osteoarthritis in the medial compartment of the knee were treated with the above surgical methods. The surgical plan was made by using the "osteotomy master" preoperatively. Intraoperatively, the OrthoPilot navigation was used to register the medial and lateral femo- ral condyles, the medial tibia platform midpoint, knee center at 90 degrees of flexion, medial and lateral ankle high points, as well as hip, knee and ankle centers to get knee varus angle and mechanical aligment by the relative position of the tibia platform. Osteotomy was per- formed according to the plan, then a spreader was used to hold the osteotomy gap until the navigation displayed the alignment adjusted to Fugisawa point. Finally, a Tomofix plate was used to fix the osteotomy. [Results] Of the 34 patients, 4 knees (4/44, 9.09%) had hinge frac- ture during operation, and 1 case had wound infection after operation. The follow-up lasted for (22.32±7.88) months. The HSS score signifi- cantly improved at last follow-up significantly compared with that before surgery (P<0.05) , with satisfaction rate of 94.12% (32/34) at lat- est follow-up. [Conclusion] This OrthoPilot navigation assisted MOWHTO is an effective surgical method for medial knee osteoarthritis, which does significantly improve the symptoms with high postoperative satisfaction.