Balance and Recovery From a Perturbation are Impaired in People With Functional Ankle Instability

Objective: To determine if differences in balance and recovery would be found between controls and participants with unilateral or bilateral functional ankle instability (FAI). Design: Cross-Sectional Study. Setting: University laboratory and Community premises. Participants: Twenty healthy participants(C), 19 participants with unilateral FAI [both the uninjured (UC) and unstable ankle (UI) were included] and 22 participants with bilateral FAI (BI). Main Outcome Measures: Balance was measured in single leg stance as: number of part foot lifts in 30 s; magnitude of medio-lateral ankle movement in two foot positions; and ability to balance on the ball of the foot. Recovery was determined by time to return to baseline medio-lateral ankle movement after a 15 degree inversion perturbation. Results: The controls lifted the foot fewer times than the other three groups [C = 12.7 ± 1.8 (mean ± SE) foot lifts, UC = 22.9 ± 2.5, UI = 25.1 ± 2.3, and BI = 21.1 ± 2.2, t-test, P = 0.006] and recovered significantly faster than the unstable ankles [C = 1.53 ± 0.42 sec (median ± SE), UI = 2.34 ± 0.30 sec, BI = 2.15 ± 0.70 sec, P < 0.02]. With FAI measured by the Cumberland Ankle Instability Tool, the external control group balanced on demi-pointe better than both instability groups (P < 0.05), and recovered quicker than all groups. Conclusion: There are differences in balance and recovery between external controls and participants with both unilateral and bilateral FAI but not between the legs of participants with unilateral FAI.