〔Abstract〕 To investigate the relationship between lower limb alignment and knee functional gait after total knee arthroplasty (TKA) for varus knee deformity . Methods A total of 94 patients with knee osteoarthritis and varus deformity underwent mechanically aligned TKA . The knee society score ( KSS) , hip-knee-ankle angle (HKA) , medial proximal tibial angle ( mMPTA) , and gait parameters ( step length , gait speed , cadence , thigh jerk acceleration , and thigh swing work) were assessed preoperatively and one month postoperatively . The correla- tion between KSS scores and changes in lower limb alignment was also analyzed . Results The KSS clinical score of the operated knee significantly improved from 39. 19 ±9. 55 preoperatively to 73 . 01 ±6. 90 postoperatively (P < 0. 001) . The KSS functional score increased from 41 . 12 ±10. 66 to 56. 33 ±7 . 41(P < 0. 001) . Postoperative gait analysis revealed significant improvements in step length , gait speed , cadence , and thigh swing work ( P < 0. 001) , while thigh jerk acceleration showed no significant change (P = 0. 525) . The HKA angle of the affected limb increased from 170. 61 ±4. 39 preoperatively to 177. 30 ±3 . 49 postoperatively ( P < 0. 001) . Similarly , the mMPTA angle increased from 83 . 95 ±3 . 32 to 89. 15 ±1 . 94 (P < 0. 001) . Correlation analysis indicated that The KSS clinical score was positively correlated with HKA ( P < 0. 001) and mMPTA ( P < 0. 05) of the lower limb force line . The KSS functional score was positively correlated with HKA (P < 0. 05) but not with mMPTA (P > 0. 05) . Conclusion In patients with severe knee osteoarthritis due to varus deformity , TKA significantly alleviates pain and improves both clinical and functional KSS scores within one month postoperatively . Restoring lower limb mechanical alignment is positively associated with joint functional recovery and enhances gait performance .