Objective: To test whether a rigid or a flexible ankle orthosis affects postural sway in single-limb stance as quantified by stabilometry.
Design: Crossover trial.
Setting: University laboratory.
Participants: Twenty-two athletes with functional ankle instability (consecutive sample of patients with recurrent ankle sprains but without mechanical instability) and 22 healthy athletes (control group of volunteers matched to age, height, weight, physical activity).
Interventions: Stabilometry in single-limb stance on a force platform. Participants were tested on each leg with and without a rigid or a flexible ankle orthosis. The order of test conditions was randomized.
Main outcome measures: Sway velocities, sway pattern, and sway area as calculated from center of pressure movements. The two groups were compared by Mann-Whitney test, and the different orthoses within each group were compared by Wilcoxon test, paired samples (type I error 5%, Bonferroni adjustment).
Results: In athletes with functional ankle instability, both a rigid and a flexible ankle orthosis significantly reduced mediolateral sway velocity. A flexible ankle orthosis also changed sway pattern significantly, by reducing the percentage of linear movements of less than 5 degrees per .01 sec.
Conclusions: In athletes with functional ankle instability, ankle orthoses reduce mediolateral sway velocity, possibly because of improved mediolateral proprioception.