Abstract:[Objective] To investigate the effect of preoperative knee varus deformity on the outcomes of total knee arthroplasty (TKA). [Methods] A retrospective study was conducted on 86 patients who received TKA for knee osteoarthritis in our hospital from April 2020 to April 2022. According to the preoperative hip-knee-ankle angle (HKAA), 54 patients had mild knee varus (≤10°), while the remaining 32 patients had moderate knee varus deformity (10°~20°). The correlation between lower limb alignment and clinical score was analyzed. [Results] All patients in both groups had TKA performed successfully without serious complications, and with no significant differences regarding perioperative data between the two groups (P>0.05). The VAS, WOMAC and HSS scores, as well as knee extension-flexion ROM significantly improved in both groups over time postoperatively (P<0.05). The mild group proved significantly better than the moderate group in terms VAS, WOMAC and HSS scores, as well as knee extension-flexion ROM before operation and 3 months postoperatively (P<0.05). Radiographically, the mild group proved significantly superior to the moderate group in terms of femorotibial angle (FTA) [(190.4±5.6)° vs (196.3±6.1)°, P< 0.001], medial proximal tibial angle (MPTA) [(73.4±3.8)° vs (67.2±3.1)°, P<0.001], posterior tibial slope (PTS) [(8.5±1.9)° vs (7.2±1.6)°, P= 0.002], mechanical axis deviation (MAD) [(38.4±1.5) mm vs (40.6±2.1) mm, P=0.002] before TKA; additionally FTA [(174.3±4.1)° vs (180.7± 5.3)°, P<0.001], MPTA [(87.6±5.3)° vs (79.3±4.5)°, P<0.001] regardless of that there was no significant difference in PTS and MAD between the two groups (P>0.05) postoperatively. As results of Pearson correlation analysis, preoperative FTA was significantly positively correlated to VAS scores (r=0.416, P=0.014) and WOMAC scores (r=0.545, P<0.001), whereas negatively correlated with ROM (r=-0.545, P<0.001). In addition, the preoperative MPTA was significantly negatively correlated to VAS scores (r=-0.452, P=0.008) and WOMAC scores (r=-0.578, P<0.001), whereas significantly positively correlated to ROM (r=0.614, P<0.001). However, there were no correlation between FTA, or MPTA with VAS, WOMAC score and ROM at the last follow-up (P>0.05). [Conclusion] The extent of knee varus deformity before surgery has considerable effect on the lower limb alignment after TKA, but has little effect on knee joint motion and knee function.