Abstract:[Objective] To investigate the effect of posterior tibial slope of the tibial component on fixed bearing unicompartmental knee arthroplasty (FB-UKA). [Methods] A retrospective study was performed on 59 patients who received FB-UKA for medial knee osteoarthritis in our hospital from August 2019 to June 2022. Based on the postoperative PTS measured on radiographs, the patients were classified into the ＜6° group, and the 6°~9° group. The clinical and imaging consequences were evaluated and compared between them. [Results] All the 59 patients had FB-UKA performed successfully with no serious complications occurred during perioperative period, and followed up for (12.6±4.9) months in mean. Compared with those preoperatively, the ROM, KSS clinical score and KSS functional score significantly increased postoperatively in both groups (P＜0.05). The 6°~9° group proved significantly superior to the ＞6° group in terms of ROM [(119.3± 9.1)° vs (113.4±10.4)°, P＜0.001], KSS clinical score [(95.3±7.8) vs (91.3±6.2), P=0.035], KSS functional score [(92.6±5.9) vs (88.9±7.6), P= 0.041] 6 months postoperatively. As for imaging, the mFTA significantly increased in both groups 1 month after surgery compared with that preoperatively (P＜0.05). There were no significant differences in postoperative mFTA, FC-VA, TC-VA between the two group (P＞0.05), whereas the ＜6° group had significantly less PTS than the 6°~9° group postoperatively [(5.2±0.3)° vs (7.9±0.4)°, P＜0.001]. [Conclusion] The PTS in 6° to 9° might be benefit to improve the range of motion and knee function in FB-UK.