Objective:To investigate MRI texture features reflecting short-term medial femoral cartilage variations after anterior cruciate ligament (ACL) reconstruction.Methods:A retrospective case series analysis was conducted referring to the data of 20 patients who received ACL reconstruction at First Affiliated Hospital of Fujian Medical University from January 2017 to January 2020 including 17 males and 3 females, aged 23-43 years [(32.1±5.4)years]. The patients were evaluated before operation and at 1, 4, 12, 24, 48 weeks after operation: (1) the region of interest (ROI) in medial femoral cartilage was divided into ROI1 (meniscus anterior horn cartilage), ROI2 (meniscus body cartilage) and ROI3 (meniscus posterior horn cartilage) according to MRI image acquisition of the affected knee. The texture feature parameters were extracted for screening and analyzing to obtain the parameters reflecting sensitivity to cartilage variations; (2) the level of urinary C-telopeptide of type II collagen (uCTX-II) was measured by ELISA. At different time points, differences in texture feature parameters were compared to screen the parameters most sensitive to cartilage variations, and uCTX-II level were compared as well. Then, Pearson correlation analysis was used to determine the correlation between texture feature parameters most sensitive to cartilage variations and uCTX-II level.Results:After screening and analyzing, the horizontal direction of gray level non-uniformity (Horzl_GlevNonU) and Skewness of histogram (Skewness) of ROI3 were selected as sensitive texture feature parameters reflecting sensitivity to cartilage variations. There were significant difference in the Horzl_GlevNonU and Skewness of ROI3 before operation and at 1, 4, 12, 24, 48 weeks after operation (all P<0.05). Meanwhile, the Horzl_GlevNonU and Skewness of ROI3 were gradually increased over time, with a more significant tendency in the Horzl_GlevNonU. The Horzl_GlevNonU of ROI3 was similar at 4 weeks and 12 weeks after operation ( P>0.05), with significant differences at other time points (all P<0.05). The Skewness of ROI3 was significantly different at 1 week and 48 weeks after operation ( P<0.05), with insignificant differences at other time points (all P>0.05). The Horzl_GlevNonU of ROI3 was selected as the most sensitive texture feature parameter reflecting cartilage variations. Significant difference was reported in uCTX-II level before operation and at 1, 4, 12, 24, 48 weeks after operation (all P<0.05). After Pearson correlation analysis, the Horzl_GlevNonU of ROI3 was positively correlated with uCTX-II level before operation and at 1, 4, 12, 24, 48 weeks after operation ( r=0.554, 0.596, 0.550, 0.632, 0.756, 0.514, P<0.05 or 0.01). Conclusion:The Horzl_GlevNonU of ROI3 is the most sensitive texture feature parameter that reflects the early variations of medial femoral cartilage after ACL reconstruction and is positively correlated with uCTX-II level.