Identifying the Most Sensitive COP Variable in Static Balance: The Impact of Chronic Ankle Instability on Postural Stability

Background Chronic ankle instability (CAI) is associated with deficits in postural control, commonly evaluated using center of pressure (COP) variables. Identifying the most sensitive COP measures for detecting balance impairments in individuals with CAI is essential for enhancing assessment and rehabilitation strategies. This study aimed to determine the most sensitive COP variables for evaluating postural stability in individuals with CAI compared to healthy controls. Methods Forty participants (20 with CAI, 20 healthy controls) performed single‐leg stance tasks on a force plate. COP variables—including average displacement, standard deviation, root mean square (RMS), range, slope, acceleration, velocity, and integral—were analyzed in anteroposterior (AP) and mediolateral (ML) directions. Repeated measures ANOVA was used for statistical comparisons. Results For the injured limb, ML RMS was significantly higher in the CAI group ( p = 0.049), whereas AP variables showed no significant differences. In the noninjured limb, ML velocity was higher in controls ( p = 0.049), whereas the integral value was greater in the CAI group ( p = 0.042). Significant foot*direction interactions were observed for acceleration, velocity ( p < 0.001), and integral ( p = 0.045). Conclusions ML RMS and integral were the most sensitive COP variables for detecting postural stability deficits in CAI individuals. These findings underscore the importance of ML‐specific balance assessments and targeted rehabilitation strategies to enhance postural control in this population.