Association between varus thrust and foot alignment and flexibility in knee osteoarthritis

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ABSTRACT Background Varus thrust (VT) is a frequently reported abnormal gait pattern in patients with medial knee osteoarthritis (KOA). VT is important to prevent KOA progression. However, there is no consensus on the relationship between VT and foot alignment and flexibility, although it has been reported that patients with KOA have pronated foot. Objective In this study, we examined the relationship between VT, foot alignment, and flexibility in patients with KOA. Methods Twenty patients with unilateral KOA were included in this study (mean age: 71.5 ± 4.7 years). KOA severity ranged from grade III (8 patients) to grade IV (12 patients) based on the Kellgren-Lawrence classification. Gait analysis using inertial sensors was performed to determine the difference between the VT of KOA side and the contralateral side without symptoms. The correlations between VT, foot alignment, and flexibility were also analyzed. Results VT was significantly greater on the side with KOA than on the contralateral side without KOA (d = 1.09, p = .002). VT was not significantly correlated with foot alignment but was significantly correlated with the arch stiffness index, which indicates foot flexibility (r = 0.642, p = .003). Conclusion This study suggests that foot flexibility may play a more significant role than foot alignment in addressing VT in patients with KOA. When performing physical therapy for VT, evaluating foot flexibility in addition to foot alignment may help reduce this condition. Further studies with larger sample sizes and more detailed statistical analyses are needed to validate these findings.