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Increased medial meniscus extrusion led to worse clinical outcomes after medial opening-wedge high tibial osteotomy



Given that no studies have assessed the correlation between improvements in medial meniscus extrusion (MME) and clinical outcomes after medial opening-wedge high tibial osteotomy (MOWHTO), the present study aimed to measure the improvement in MME after MOWHTO and to investigate the correlation between the remaining postoperative MME and MOWHTO clinical outcomes by subgroup analysis.


This study included 79 patients (80 knees) who underwent MOWHTO with a minimum follow-up of 2 years. MME was measured pre- and postoperatively through magnetic resonance imaging after an average of 19.8 months following MOWHTO surgery. Clinical outcomes were evaluated according to the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Tegner Activity Scale, and the Short-Form 36 questionnaire. In subgroup analysis, postoperative MME was classified into non-pathologic (≤ 3 mm) and pathologic (> 3 mm) groups. The clinical outcomes of the two groups were compared using Mann–Whitney U tests. A regression analysis was performed to determine the preoperative and postoperative characteristics associated with the improvement of MME.


The mean (± standard deviation) values for pre- and postoperative MME were 3.6 (± 1.8) mm and 2.8 (± 1.5) mm, respectively (p < 0.001). In the subgroup analysis of postoperative MME, the non-pathologic group showed better improvement of KOOS than the pathologic group. Preoperative hip-knee-ankle angle was correlated with the improvement of medial meniscal extrusion in both univariate (p = 0.049) and multivariate (p = 0.015) analyses.


The MME improved after MOWHTO, and the clinical outcomes were better for patients with a postoperative MME of less than 3 mm than for those with more than 3 mm. MME improvement after MOWHTO was correlated with preoperative varus alignment of the lower extremities.

Level of evidence

III (Retrospective cohort study).

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Fig. 1
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Fig. 4



Medial meniscus extrusion


Medial opening-wedge high tibial osteotomy


Knee injury and osteoarthritis outcome score

HKA angle:

Hip-knee-ankle angle


High tibial osteotomy




Magnetic resonance imaging


Intra-class correlation coefficient


Short-Form 36


Body mass index




Physical component summary


Mental component summary


Medial proximal tibial angle


Posterior tibial slope angle


Minimal clinically important difference


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The authors declare that there they have non-financial competing interests.

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All the authors contributed to the study conception and design. Material preparation, and data collection and analysis were performed by C-HL, H-YY, and J-KS. Review, editing, and supervision by J-KS.

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Correspondence to Jong-Keun Seon.

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This retrospective chart review study involving human participants was in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The Human Investigation Committee (IRB) of Hwasun Chonnam National University Hospital approved this study.

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Lee, CH., Yang, HY. & Seon, JK. Increased medial meniscus extrusion led to worse clinical outcomes after medial opening-wedge high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc (2022).

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  • Clinical outcomes
  • High tibial osteotomy
  • Knee osteoarthritis
  • Medial opening-wedge
  • Meniscal extrusion