Reconstructing Physiological Knee Medial Tightness in Total Knee Arthroplasty is Associated with Superior Clinical Outcomes in Asian Population: A Retrospective Cohort Study with Finite Element Analysis

Objective For Asian populations with physiological varus, optimal gap balance in total knee arthroplasty (TKA) remains debated. This study evaluated whether preserving physiological medial is superior to absolute balance. Methods In this retrospective study of 252 knees, patients undergoing primary posterior‑stabilized (PS) TKA were grouped by postoperative medial‑lateral gap difference. Clinical osteoarthritis assessment scores including KSS (Knee Society Score), WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) and FJS-12 (Forgotten Joint Score) were evaluated, comparing postoperative outcomes and their improvements after at least one year of follow-up. Subgroup analyses considered age, varus severity, and BMI. Finite element analysis (FEA) of different balance models were performed for load distribution and stress. Results Both the medially tight and balanced groups achieved superior outcomes compared with the laterally tight group. Moreover, patients with a gap difference of 1.0–1.5 mm (medially tight) demonstrated greater improvements in total, functional, and clinical KSS scores than the balanced group (all p < 0.05). Among patients > 70 years, medial tightness provided a substantial functional improvement (KSS functional improvements: 37.9 ± 11.7 vs. 26.1 ± 9.84, p = 0.011). Besides, for patients with hip-knee-ankle angle > 10°, 0.5–1.0 mm gap difference (medially tight) contributed to fewer clinical symptoms (KSS clinical improvements:54.2 ± 11.4 vs. 43.9 ± 14.4, p = 0.040). FEA indicated that the medially tight model restored a more physiological load and favorable stress distribution. Conclusion For Asian patients undergoing PS TKA, reconstructing physiological medial tightness is associated with better functional recovery and a more physiological biomechanical environment than absolute balance reconstruction.