CHANGES IN HINDFOOT ALIGNMENT AFTER TOTAL KNEE ARTHROPLASTY IN KNEE OSTEOARTHRITIC PATIENTS WITH VARUS DEFORMITY-A PROSPECTIVE COMPARATIVE STUDY

Abstract

Background: Varus deformity of the knee in osteoarthritis (OA) profoundly alters lower limb biomechanics, propagating compensatory deformities to the hindfoot. Total knee arthroplasty (TKA) corrects coronal malalignment, but its downstream effect on hindfoot alignment remains incompletely characterized. Understanding these changes is essential for comprehensive perioperative planning. Objectives: To evaluate serial changes in hindfoot alignment following TKA and to determine correlations between the severity of pre-operative varus deformity and magnitude of hindfoot correction. Methods: A prospective comparative cohort study was conducted on 50 patients who underwent primary TKA for knee OA with varus deformity between June 2024 and June 2025 at Saveetha Medical College and Hospital. Patients were stratified into Group A (varus ≤10°, n=26) and Group B (varus >10°, n=24). Standardized weight-bearing hindfoot radiographs, including calcaneal valgus angle, talar tilt angle, and tibiotalar tilt angle, were obtained pre-operatively and at 6 weeks, 3 months, 6 months, and 12 months post-operatively. Clinical outcomes were assessed using the Knee Society Score (KSS), Visual Analogue Scale (VAS), and Oxford Knee Score (OKS). Statistical analyses included repeated-measures ANOVA, Pearson correlation, and multivariate regression. Results: All patients demonstrated progressive improvement in hindfoot alignment following TKA, with the most significant correction occurring within the first three months. The mean calcaneal valgus angle reduced from 5.2° ± 1.8° to 2.1° ± 1.0° in Group A (p<0.001) and from 8.9° ± 2.3° to 3.3° ± 1.3° in Group B (p<0.001). A strong positive correlation existed between pre-operative varus magnitude and pre-operative calcaneal valgus angle (r=0.74, p<0.001). Group A demonstrated significantly superior hindfoot correction and clinical outcomes at 12 months compared to Group B (KSS 87.4 vs. 81.2, p=0.003). Conclusions: TKA effectively corrects varus-associated hindfoot deformity in a significant proportion of patients, particularly those with mild-to-moderate varus. Patients with severe varus deformity (>10°) exhibit greater residual hindfoot malalignment despite adequate knee correction, suggesting that concomitant hindfoot assessment and targeted rehabilitation are warranted in this cohort.