Medial Unicompartmental Knee Arthroplasty vs. High Tibial Osteotomy for Isolated Medial Knee Osteoarthritis: A Propensity-Matched Study of Clinical Outcomes.

Abstract

To compare functional and radiographic outcomes between medial opening-wedge high tibial osteotomy (HTO) and medial unicompartmental knee arthroplasty (UKA) in isolated medial compartment osteoarthritis, incorporating minimal clinically important difference (MCID) thresholds for clinical interpretation. A retrospective propensity score-matched cohort study of 52 patients (26 HTO, 26 UKA) treated between 2016 and 2021 was performed. Outcomes included Oxford Knee Score (OKS, primary), VAS pain, Knee Society Score (KSS) Function, radiographic alignment, complications, and revision-free survival. At a mean follow-up of 28.4 ± 4.2 months, baseline characteristics were balanced. UKA achieved superior OKS at 24 months (40.1 vs. 34.8, mean difference 5.3, <i>p</i> = 0.001), exceeding the MCID threshold. Pain reduction favored UKA but did not reach MCID (mean difference 1.1, <i>p</i> = 0.002). KSS Function differences were statistically significant but below MCID. Radiographic correction was greater with HTO (valgus 3.9° vs. 0.9°, <i>p</i> < 0.001). Revision rates were 3.8% for HTO vs. 7.7% for UKA (<i>p</i> = 0.55). UKA provided clinically meaningful functional improvement compared with HTO at 2 years, while HTO offered superior mechanical axis correction. Procedure choice should be individualized based on age, activity level, and patient expectations. Level of Evidence: III (retrospective cohort study).