High tibial osteotomy (HTO) can cause alterations in patellar height, depending on the surgical technique, the amount of correction and the postoperative management. Alterations in patella location after HTO may lead to postoperative complications. However, information on changes in dynamic patellar kinematics following HTO is very limited. We conducted a biomechanical study, to analyze the effect of open (OWO) and closed wedge osteotomy (CWO) on patellar tracking. Using an inventive experimental set-up, we studied the 3D dynamic patellar tracking in ten cadaver knees before and after valgus HTO. In each specimen, corrections of 7 degrees and 15 degrees of valgus according to, both, the OWO and CWO technique, were performed. Patellar height significantly increased with CWO and decreased with OWO. Both, OWO and CWO led to significant changes in the patellar tracking parameters tilt and rotation. We also found significant differences between OWO and CWO. Valgus high tibial osteotomy increased the medial patellar tilt and reduced the medial patellar rotation. These effects were more profound after OWO. No significant differences were found for the effect on medial-lateral patellar translation. These observations can be taken into consideration in the decision whether to perform an OWO or a CWO in a patient with medial compartment osteoarthritis of the knee.