Abstract: Objective To investigate the correlation between medial meniscus injury and mediopatellar plica(MPP) under arthroscopy. Methods Eighteen patients with medial meniscus injury who received arthroscopic treatment in our hospital from January 2016 to January 2018 were collected. Medial meniscus plasty or suture was performed, and MPP was removed under arthroscopy. According to the presence or absence of MPP under arthroscopy, the patients were divided into two groups. According to whether there is pathological MPP under arthroscopy, the patients were divided into two groups. Lysholm score was used for knee function before and after surgery. Covariance analysis was used to compare the data, and Spearman analysis was used to analyze the correlation between the two factors. Results Before surgery, the preoperative Lysholm score of the no MPP group(38.36±3.12) was higher than that of the MPP group(30.43±1.75), and after surgery, the postoperative Lysholm score of the no MPP group(78.91±4.52) was higher than that of the MPP group(70.36±3.71). Before surgery, the preoperative Lysholm score of MPP group A and B(38.37±3.23) was higher than that of C and D group(30.78±1.10), and after surgery, the postoperative Lysholm score of MPP group A and B(79.75±2.90) was higher than that of C and D group(70.27±2.81, all P<0.05). Spearman correlation analysis showed that the postoperative Lysholm score was negatively correlated with MPP content(correlation coefficient r=-0.792, P<0.05). Conclusion MPP affects the efficacy of patients with medial meniscus injury of the knee joint, and accurate removal of MPP, especially type C and D, is required under arthroscopy.