Background <p>Rotational alignment changes following high tibial osteotomy (HTO) can alter patellofemoral joint biomechanics, potentially leading to adverse clinical outcomes. This study aimed to compare rotational alignment changes and clinical outcomes between two different types of biplanar medial opening-wedge HTO: proximal tubercle osteotomy (PT-HTO) and distal tubercle osteotomy (DT-HTO).</p> Methods <p>A total of 178 patients who underwent medial opening-wedge HTO for medial compartment osteoarthritis between January 2020 and March 2023, with a minimum follow-up of two years, were retrospectively identified. Patients were stratified into two groups based on the direction of the second-plane osteotomy: PT-HTO (<i>n</i> = 136) and DT-HTO (<i>n</i> = 42). Propensity score matching was performed based on age, sex, body mass index, preoperative Kellgren–Lawrence grade, preoperative mechanical hip-knee-ankle angle, and correction angle, yielding 42 matched patients in each group. Radiological assessments were conducted using preoperative and postoperative lower extremity computed tomography scans. The primary outcome measure was the change in rotational alignment (tibial torsion angle, knee rotation angle, and knee-ankle rotation angle). Secondary outcomes included the tibial tuberosity–trochlear groove (TT–TG) distance and clinical outcomes assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Kujala score.</p> Results <p>The mean tibial torsion angle significantly decreased in both groups compared to preoperative values, with reductions of − 3.8° in the PT-HTO group and − 1.4° in the DT-HTO group, with a marginally significant difference between the groups (<i>p</i> = 0.062). The knee rotation angle exhibited a greater reduction following PT-HTO than DT-HTO (− 2.4° vs. −1.4°; <i>p</i> = 0.046), indicating increased external rotation of the proximal fragment after PT-HTO. The TT–TG distance increased in the PT-HTO group but was preserved in the DT-HTO group, with a significant difference in mean change between the groups (2.1&#xa0;mm vs. −0.2&#xa0;mm; <i>p</i> &lt; 0.001). Patellar height significantly decreased in the PT-HTO group, as reflected by reductions in the Blackburne–Peel ratio (− 0.14; <i>p</i> = 0.001) and Caton-Deschamps index (− 0.16; <i>p</i> &lt; 0.001), whereas the DT-HTO group maintained preoperative patellar height. At a mean follow-up of 31.2 months, the DT-HTO group showed significantly better postoperative clinical outcomes, with higher KOOS pain scores (82.6 vs. 74.0; <i>p</i> = 0.030) and Kujala scores (72.3 vs. 65.7; <i>p</i> = 0.028) compared to the PT-HTO group.</p> Conclusions <p>DT-HTO resulted in reduced rotational alignment changes and superior patellofemoral joint alignment compared to PT-HTO, leading to improved clinical outcomes.</p> Level of evidence <p>Retrospective comparative study; Level III.</p>