PurposeThis study investigated whether inducing valgus alignment and shifting the load laterally through high tibial osteotomy (HTO) alone decreases the extent of medial meniscus extrusion (MME) in the setting of medial meniscus posterior root tear(MMPRT) using ultrasound evaluation. MethodsEight fresh-frozen human cadaveric knee specimens were tested using a six-degree-of-freedom robotic testing system and ultrasound. Each specimen was tested in five conditions: (1) intact, (2) MMPRT, (3) medial meniscus repair (MMR), (4) combined medial open-wedge HTO + MMR, and (5) HTO + MMPRT. Measurements were obtained over the medial collateral ligament (MCL, central image) and posterior to the MCL (posterior image) with a 250 N axial load at 0°, 30°, and 90° of knee flexion. Statistical analysis was performed using a two-factor repeated-measures ANOVA. ResultsMME was significantly greater in HTO + MMPRT(0°: 2.44 ± 0.41mm, 30°: 2.47 ± 0.37mm, 90°: 2.41 ± 0.28mm) than HTO + MMR in central images (mean difference +0.83 mm, p < .001). No significant difference was found between HTO + MMPRT and MMPRT in MME . MMR had significantly less MME than MMPRT (mean difference -0.58mm, p < .001, posterior image at 0°and central image at 90°, p=.002). HTO + MMR showed significantly less MME than MMR alone at 30° and 90° knee flexion in central image (30°: -0.38 ± 0.05mm, 90°: -0.45 ± 0.06mm, p < .001) and 90° knee flexion in posterior image (-0.38 ± 0.08mm, p = .004). ConclusionHTO alone did not decrease MME in the setting of MMPRT, while MMR alone decrease MME after MMPRT. Additionally, HTO + MMR decreases MME aftrer MMPRT compared to MMR alone, although the clinical significance was uncertain. Clinical RelevanceThe findings of this study provide clinicians with valuable insights for improving MME. HTO alone does not decrease MME in cases of MMPRT.