The Relationship between the Ability to Cope with Unexpected Perturbations and Mechanical and Functional Ankle Instability

We aimed to examine the associations between ankle instability, identified by mechanical and functional assessments, and an individual’s ability to cope unexpected perturbations. Sixty students were assessed for five different mechanical/functional ankle instability assessments: the Cumberland Ankle Instability Tool (CAIT), history of previous ankle sprains, the Ankle Instability Instrument (AII) questionnaires, proprioception ability, and mechanical instability. The point where participants lost postural balance due to an unexpected perturbation was recorded when participants were standing on BalanceTutor-Treadmill^® with eyes open-SO, eyes closed-SC, tandem-dominant-leg forward-TD, tandem non-dominant-leg forward-TND, single-leg same side-SLSS, single-leg opposite side-SLOS and walking. Significant correlations were found between: CAIT and perturbation in the TND-position; AII scores and perturbations in TD and TND positions; ankle sprains and perturbations in SC, ND, and NTD positions; and proprioception ability and perturbations in SO, SC, TD, TND, and walking (p < 0.05). No correlations were found between mechanical assessments and perturbations. Survival-analyses showed significant differences in coping with perturbations between individuals identified with CAI in 4/5 mechanical/functional assessments compared to those with no-CAI in 4/5 assessments (p < 0.05). Functional ankle instability and proprioception ability were associated with the ability to cope with unexpected perturbations when starting from different standing/walking positions. Individuals with ‘stable’ ankles in most mechanical/functional assessments had better ability to cope perturbations than those with ‘unstable’ ankles.