Discrimination Between Mechanical and Functional Ankle Instability, and Copers: A Questionnaire-Based Analysis.

Objective: This study aimed to differentiate subgroups of chronic ankle instability (CAI), including mechanical ankle instability (structural damage), functional ankle instability (FAI: neuromuscular deficits), Copers (individuals who recovered functional stability without recurrent symptoms), and controls (healthy individuals), using a validated questionnaire set (Cumberland ankle instability tool [CAIT], identification of functional ankle instability [IdFAI], ankle instability instrument [AII], foot and ankle ability measurement [FAAM]/Activities of Daily Living, FAAM/Sports). Additionally, we sought to present a standardized scoring system to classify CAI, Copers, and control participants.

Design: Case-control study.

Methods: A total of 104 people participated in the study, including 26 mechanical ankle instability, 26 functional ankle instability, 26 Copers, and 26 healthy controls. The Kruskal-Wallis test was used for analysis, and the Mann-Whitney test was used for post hoc tests. The cutoff value for each group was confirmed using the receiver operating characteristic curve.

Results: Analyses comparing the CAI, Copers, and control groups revealed significant differences in CAIT (P < .001), IdFAI (P < .001), AII (P < .001), FAAM/Activities of Daily Living (P < .001), and FAAM/Sports (P < .001). The cutoff values for each group were confirmed for CAIT, IdFAI, AII, FAAM/Activities of Daily Living, and FAAM/Sports. For CAIT, it was 0 to 8.5 mechanical ankle instability, 8.6 to 23 for functional ankle instability, 24 to 29.5 for Copers, and 29.6 to 30 for control.

Conclusion: These findings support using CAIT, IdFAI, and AII to classify CAI subtypes and identify Copers. Questionnaire-based cutoff values may assist rehabilitation planning and clinical decision-making. A CAIT score below 8.5 may indicate surgical consideration, supported by comprehensive clinical assessment.