Contributing Factors to Chronic Ankle Instability

Abstract

The development of repetitive ankle sprains and persistent symptoms after initial ankle sprain has been termed chronic ankle instability (CAI). Two contributing factors to CAI are functional instability and mechanical instability. The relationship of the specific insufficiencies to each other, or how they individually contribute to ankle instability, has not been examined. There is not a clear indication of what measures are most important in discriminating between individuals with and without CAI. Therefore, the purpose of this study was to examine side-to-side differences for the following variables: ankle laxity and hypomobility, static and dynamic balance, ankle and hip strength, selected lower extremity malalignments, and ITB flexibility. Thirty subjects with unilateral CAI and 30 healthy controls were tested. To look at differences within the ankles of the CAI and control group symmetry indices comparing the involved and uninvolved sides of each subject were calculated for each dependent variable and compared between groups using independent t-tests. Eight variables were identified as being significantly different between groups and were entered into a discriminant analysis. These 8 factors explained 46.5% of CAI group membership. The measures significantly predictive of CAI group membership were decreased anterior reach, diminished plantar flexion peak torque, decreased posterior medial reach, and more inversion rotation. These four variables correctly predicted group membership in 80.0% of CAI subjects and 73.3% of healthy subjects. The results of this study elucidate the specific measures that best discriminate between subjects with and without CAI. Measures of both mechanical and functional insufficiencies significantly contribute to the etiology of CAI.