Quantifying levels of function between different subgroups of chronic ankle instability.

The purpose of this original investigation was to determine if selected sensorimotor, mechanical, and self-reported measures are different among chronic ankle instability (CAI) subgroups, healthy control participants, and lateral ankle sprain copers (LAS-Copers). Ninety-four participants volunteered and were categorized into perceived ankle instability (PI) alone (n = 13), recurrent ankle sprains (RAS) alone (n = 12), PI in combination with RAS (PI-RAS; n = 25), LAS-Copers (n = 18), and controls (n = 26). Participants completed self-assessed global, regional, and psychological health-related quality-of-life (HRQOL) questionnaires and assessments of sensorimotor function and mechanical joint laxity. One-way ANOVAs were performed with the intention of reducing the number of original outcomes into a smaller number of predictor variables. Discriminant functional analysis was used to establish which specific measures best differentiate between groups. Eight outcome measures from neural excitability, postural control, static postural control, and HRQOL showed a significant differentiation between five groups (Wilk's λ = 0.26, χ232  = 114 45, P < 0.001, canonical correlation = 0.80) and correctly determined only 58.1% of group membership, and the PI-RAS and control groups were the only fit in the proposed model. A different model or other sensorimotor outcomes from more dynamic and complex tasks may be needed for the PI, RAS, and LAS-Coper groups.