Abstract:[Objective] To investigate the correlation between lower limb alignment parameters and the extent of meniscal medial extrusion (MME) in knee osteoarthritis (KOA). [Methods] A total of 307 patients with KOA treated in our hospital from 2022 to 2023 were included in this study. Univariate comparison and Pearson correlation analysis were used to analyze the relationship between MME and lower limb alignment, while ROC curve analysis was used to evaluate the predictive value of lower limb alignment parameters for MME degree. [Results] As results of MME measured on MRI, 307 knees were divided into two groups. Of them, 212 knees with MME>0.3 cm were marked as the severe group, accounting for 69.1%, while othor 95 knees with MME≤0.3 cm were as the mild group, accounting for 30.9%. In term of univariate comparison, the severe group proved significantly greater than the mild group regarding to AMA [(6.9±1.0)° vs (5.9± 0.8), P<0.001], JLCA [(5.4±1.3)° vs (2.9±1.1)°, P<0.001], mLDFA [(88.1±2.8)° vs (83.5±4.2)°, P<0.001], while the former significantly less than the latter in MPTA [(86.1±3.0)° vs (86.6±3.1)°, P=0.005], mHKA [(1.6±0.8)° vs (2.9±1.9)°, P<0.001]. In term of pairwise correlation, the MME was positively correlated with AMA, JLCA and mLDFA (P<0.05), while was significantly negatively correlated with FTA, MPTA and mHKA (P<0.05). ROC analysis indicated that AMA, JLCA and mLDFA with values higher than 6.33°, 3.55 ° and 86.34° predicted MME≥0.3 cm got the area under cuve (AUC) of 0.807, 0.954 and 0.791 respectively. [Conclusion] AMA, JLCA and mLDFA are closely related to the degree of MME in KOA, and can be used as important parameters to evaluate the severity of MME.