Original Article

An increase in the medial proximal tibial angle of 95° or greater after opening wedge high tibial osteotomy does not necessarily lead to excessive knee joint line obliquity of 5° or greater

¹ Department of Orthopaedic Surgery, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
² Department of Orthopaedic Surgery, Yokohama City University Medical Center, 4-57 Urafune-cho, Minami-ku, Yokohama 232-0024, Japan

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it. ; This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 5 November 2026
Accepted: 31 March 2026

Abstract

Introduction: The relationship between medial proximal tibial angle (MPTA) overcorrection and knee joint line obliquity (KJLO) after opening wedge high tibial osteotomy (OWHTO) remains controversial. Though excessive valgus correction (MPTA ≥ 95°) has been associated with abnormal joint line inclination, the extent to which this affects postoperative alignment and whether overcorrection necessarily results in excessive KJLO (≥5°), which has been associated with increased shear stress on the articular cartilage, is unclear. Methods: A total of 300 knees undergoing isolated OWHTO were retrospectively reviewed. Postoperative KJLO and MPTA were measured using full-length standing radiographs. Knees were stratified into MPTA <95° and ≥95° groups. Correlations between postoperative MPTA and KJLO were analyzed, and in the overcorrected (MPTA ≥ 95°) group, logistic regression and receiver-operating characteristic (ROC) curve analyses were performed to identify preoperative predictors of postoperative KJLO ≥ 5°. Results: Postoperative MPTA showed a significant positive correlation with KJLO (r = 0.61, p < 0.001). However, 52.5% of knees with MPTA ≥ 95° maintained KJLO < 5°, indicating that overcorrection does not necessarily cause excessive joint line inclination. Multivariable analysis identified preoperative lateral distal femoral angle (LDFA), knee joint line convergence angle (KJLCA), and ankle joint line obliquity (AJLO) as independent predictors of postoperative KJLO ≥ 5° in knees with MPTA ≥ 95° (p < 0.01). ROC curve analyses showed that AJLO ≥ 5.6°, LDFA ≥ 88.9°, and KJLCA ≥ 4.5° were the cutoff values predicting KJLO ≥ 5°. Conclusions: Although postoperative MPTA correlates with KJLO, more than half of the overcorrected cases maintained acceptable joint line inclination. Preoperative AJLO, LDFA, and KJLCA are key parameters for predicting postoperative KJLO ≥ 5° in knees with MPTA ≥ 95°, highlighting the importance of comprehensive preoperative alignment assessment when planning OWHTO.