Postural control differs between those with and without chronic ankle instability

Despite a history of a lateral ankle sprain, some individuals (copers) return to high-level activities (i.e. jumping, pivoting) without recurrent injury or loss of function while others develop chronic ankle instability (CAI). Understanding the differences between these groups may provide insight into the mechanisms of CAI. The objectives of this investigation were to: (1) compare traditional center of pressure [COP], time-to-boundary [TTB], and center of pressure–center of mass [COP–COM] moment arm measures of postural control among controls, established copers, and subjects with CAI and (2) determine the accuracy of these postural control measures at discriminating between established copers and subjects with CAI using receiving operating characteristic curves. 48 subjects (control = 16, coper = 16, CAI = 16) completed two, 30-s trials of single-leg stance on a force plate with their eyes open. Coper and CAI subjects stood on their involved limb while controls stood on a matched limb. The results indicated that mediolateral (p < 0.01) and anteroposterior (p < 0.01) COP velocity was greater in individuals with CAI relative to both copers and controls. Similarly, the peak COP–COM moment arm in the anteroposterior direction (p < 0.01) and the resultant mean COP–COM moment arm (p < 0.01) were increased in individuals with CAI relative to copers. These measures also reached asymptotic significance (p < 0.05) indicating that they successfully discriminated between established copers and individuals with CAI.