Postoperative Lower Knee Adduction Moment Limits Patient-Reported Outcome Improvements After Medial Opening Wedge High Tibial Osteotomy

Objectives: The knee adduction moment (KAM) is a dynamic biomechanical marker linked to medial joint loading and the progression of medial compartment osteoarthritis 1. However, its association with patient-reported outcome measures (PROMs) after realignment procedures remains insufficiently understood. This study evaluated the relationship between postoperative KAM and PROMs following medial opening-wedge high tibial osteotomy (MOWHTO) and identified the KAM threshold associated with clinically meaningful improvement. Methods: A retrospective analysis was conducted on 40 patients (35 males, 5 females; mean age: 49.0 years) with medial compartment knee osteoarthritis who underwent MOWHTO. Radiographic assessments, including the hip-knee-ankle (HKA) angle, were performed preoperatively and six months postoperatively. Dynamic 3D gait analysis was used to assess the first peak of KAM (KAM 1st peak) at the same time point. PROMs were evaluated using the Western Ontario and McMaster Universities Arthritis Index (WOMAC) total score preoperatively and 12 months postoperatively 2. Pearson correlation analysis examined the relationship between postoperative KAM 1st peak and ΔWOMAC total score (preoperative to postoperative improvement). Receiver operating characteristic (ROC) analysis was performed to determine the optimal postoperative KAM 1st peak cutoff for achieving the minimal clinically important difference (MCID) 3. Results: The mean postoperative HKA angle was 182.8° ± 1.4°. KAM 1st peak significantly decreased by 53%, from 50.9 ± 12.5 Nm preoperatively to 23.6 ± 7.1 Nm postoperatively (p < 0.001). A significant positive correlation was observed between postoperative KAM 1st peak and ΔWOMAC total score (r = 0.325, p = 0.020). ROC analysis identified 25.7 Nm as the optimal postoperative KAM 1st peak cutoff for MCID, with 57% sensitivity and 84% specificity. The median postoperative HKA angle significantly differed between the groups, with the lower KAM group (<25.7 Nm) showing a median angle of 183.2° (182.5–184.3°), compared to 182.1° (180.9–183.4°) in the higher KAM group (≥25.7 Nm) (p = 0.028), indicating greater valgus correction in the lower KAM group. Conclusions: While reducing KAM is the primary goal of MOWHTO and is associated with improved PROMs, excessive reduction (<25.7 Nm), corresponding to a median HKA angle of 183.2°, appears to limit short-term improvements. Integrating dynamic gait assessments with static radiographic evaluations may enhance understanding of the relationship between achieved alignment and postoperative outcomes and help refine correction prescription to optimize the outcomes of osteotomy.