Objective To study the clinical application of knee joint locking mechanism in Oxford Ⅲ generation unicondylar prosthesis replacement.Methods 73 patients with AMOA admitted to our hospital from January 2020 to January 2021 were divided into two groups according to random number table (conventional method group and new method group).The conventional method group (38 cases) underwent vertical tibial osteotomy against the anterior cruciate ligament，and the new method group (35 cases) had an average internal rotation of about 5 °~10 ° during vertical tibial osteotomy compared with the traditional method group.The Oxford Ⅲ monocondyle prosthesis was installed according to the new surgical osteotomy design.Statistical analysis was performed using SPSS 26.0 software to compare the results of the two methods in the postoperative hospital for special surgery，HSS)，visual analogue scale (visual analogue scale，VAS)，western Ontario and mcmaster universities osteoarthritis index (WOMAC)and associated differences in threedimensional knee gait.Results During postoperative followup，the HSS，WOMAC score and VAS of the two groups were improved compared with those before surgery，with statistical significance (P＜0.05).HSS，WOMAC score and standing VAS of the new method group were improved compared with the traditional method group at 3 d，1 months，6 months and 12 months after surgery，and the differences were statistically significant (P＜0.05).There was no statistically significant difference in sitting VAS between the two groups at postoperative follow-up (P＞0.05).There was statistical significance in the excellent and good rate of the two groups at the last follow-up (P＜0.05).At the last follow-up，three-dimensional gait analysis of knee joint was performed，and the result showed that the internal and external rotation Angle of the new method was higher than that of the conventional method，and the difference was statistically significant (P＜0.05).Conclusion Combined with the locking mechanism of the knee joint，the average internal rotation of the tibial end during vertical osteotomy is about 5°~10° compared with the traditional method，which can improve the functional score of the knee joint and achieve a higher excellent and good rate.At the same time，compared with the conventional method，this method can make the internal and external rotation more close to the normal range of physiological movement.