Study Design Cohort study.

Objectives Determine if individuals with unilateral Chronic Ankle Instability (CAI) exhibit deficits on clinician-oriented measure of postural control.

Background Repetitive occurrences of lateral ankle sprains may result in long-term functional impairments, residual symptoms, and may lead to CAI. Postural control depends on feedback and feedforward systems, which is altered in individuals with CAI.

Methods and Measures Forty individuals with unilateral CAI based on the Identification of Functional Ankle Instability (IdFAI) by scoring greater than 11 and with no ankle injury in the past three months (17 female, 23 male; 20.2±1.5 years; 1.7±0.1 m; 79.2±11.5 kg; IdFAI: 19.5±4.2) were recruited. Forty were classified as uninjured controls based on the IdFAI by scoring 0 and never sustaining an ankle injury (17 female, 23 male; 21.5±1.3 years; 1.7±0.2 m; 75.7±15.8 kg; IdFAI: 0±0). Participants completed the Y-balance test (anteromedial, posteromedial and posterolateral directions). The average of three trials for each direction, normalised to the participant’s leg length as a percent was calculated. Only the CAI leg and matched control group leg was used for analysis. The dependent variable was each direction on the Y-balance test and the independent variable was group (CAI and control). A MANOVA was conducted for all dependent variables, alpha level was set at p<0.05.

Results Based on published effect sizes for the Y-balance test (0.8), alpha 0.05, power 0.95, two groups, three measures, and a correlation among measures of 0.5, the sample size needed per group was 15. There were no between-group differences for any reach direction (anteromedial: CAI: 66.3±7.6, CON: 66.8±7.8; posteromedial: CAI: 100.7±8.3, CON:102.5±8.9; and posterolateral: CAI: 100.6±10.7, CON: 101.8±10.2) p>0.05.

Conclusion These data suggest that clinician-oriented measures of postural control outcomes cannot discriminate between CAI and uninjured controls. Future research needs to develop clinician-oriented measures capable of detecting postural control impairments in individuals with CAI.