Objective To investigate the effect of sagittal plane wedge opening on the posterior tibial slope(PTS) during the surgical treatment of knee osteoarthritis (KOA)using medial openingwedge high tibial osteotomy(MOWHTO).Methods A retrospective analysis was conducted on clinical data from 63 KOA patients who underwent MOWHTO treatment in Shandong Hospital of Traditional Chinese Medicine between January 2019 and July 2020.The experimental group included 31 patients，consisting of 13 males and 18 females，with an average age of (56.29±3.49)years and a mean body mass index (BMI) of (26.48±1.77)kg/m².The patients in this group underwent tibial osteotomy with approximate sagittal plane wedge opening between the lower 1/2 to 2/3 of the tibia.The control group included 32 patients，consisting of 14 males and 18 females，with an average age of (55.66±2.66)years and a mean BMI of (27.13±2.39)kg/m²，who underwent conventional osteotomy.Before the surgery，there were no statistically significant differences (P＞0.05) between the two groups regarding gender，age，BMI，preoperative visual analogue scale (VAS) pain scores，hospital for special surgery(HSS) scores，Lysholm scores，PTS，or other baseline characteristics.The first X-ray examination was performed within one week after surgery，and PTS was measured during the final follow-up，which was then compared with the preoperative measurement.The knee joint pain from patients and the functional status were also assessed using VAS scores，HSS scores，and Lysholm scores before surgery and at the final follow-up.Results Both groups of patients successfully completed the follow-up，with a follow-up period ranging from 22 to 32 months，with an average of (26.81±2.12)months.No complications such as vascular or neural injuries or lower limb venous thrombosis were observed in either group.At the final follow-up，both groups showed significant improvements in VAS scores，HSS scores，and Lysholm scores compared to preoperative values，with statistically significant differences (P＜0.05).However，there were no significant differences between the two groups at various time points (P＞0.05).The PTS in the experimental group showed no statistically significant differences at different time points (P＞0.05).In contrast，patients in the control group had a significant increase in PTS after surgery and at the final follow-up (P＜0.05).At both postoperative and final follow-up time points，the experimental group had significantly lower PTS values than the control group，with statistically significant differences (P＜0.05).Conclusion The use of OWHTO for KOA treatment effectively alleviates knee joint pain and improves functionality.Additionally，the utilization of sagittal plane wedge opening effectively prevents an increase in PTS.