Study Design Case-Control Study.

Objectives To determine the extent that strength, dorsiflexion range of motion (DFROM), self-selected gait velocity and star excursion balance test (SEBT) performance contribute to Identification of Functional Ankle Instability (IdFAI) score variance in individuals with chronic ankle instability (CAI).

Background Mechanical and sensorimotor impairments have been well documented and associated with the decreased self-reported instability among individuals with CAI. Yet, little information exists for which mechanical and sensorimotor impairments contribute most to the self-reported instability associated with CAI. Identifying the impairments that contribute to self-reported instability will help direct effective evidence-based rehabilitation strategies.

Methods and Measures Based on the International Ankle Consortium guidelines, 30 participants with CAI (24.9±4.7 years; 165.9±9.3 cm; 73.6±15.5 kg) and 29 healthy-controls (HC) (25.4±5.7 ys; 168.8±9.4; 68.5±16.5 kg) volunteered. Primary outcomes included weight-bearing DFROM (cm); dorsiflexion, plantar flexion, knee and hip extension, and hip abduction peak isometric torque (Nm/Kg); self-selected gait velocity (cm/sec); and the average normalised reach distance for the SEBT- anterior (SEBT-A), posteromedial (SEBT-PM), and posterolateral (SEBT-PL) reach directions. Separate Independent T-tests were used to identify group differences. Explanatory variables that significantly correlated with the criterion variable were then entered into a backwards multiple linear regression to predict the variance in self-reported instability. Significance was set a priori at p<0.05.

Results Participants with CAI scored higher on the IdFAI and had decreased dorsiflexion, plantar flexion, knee and hip extension torque, self-selected gait velocity, weight-bearing DFROM and normalised SEBT-A and SEBT-PM reach distances compared to HC (p<0.05). The backwards multiple linear regression indicated that lower knee extension torque, SEBT-A and self-selected gait velocity were significantly associated with a higher IdFAI (R²=0.534, p<0.001) score in individuals with CAI.

Conclusion Therapeutic interventions that target knee strength, the SEBT-A reach direction, and optimisation of gait performance may be beneficial to treating self-reported instability in those with CAI.