Movement Variability in Chronic Ankle Instability During an Anterior Single Leg Jump Landing

Abstract

Chronic ankle instability (CAI) commonly develops following lateral ankle sprain, but factors influencing its development are unclear. Movement variability, suggested as a possible contributing factor to CAI, may influence injury mechanisms. PURPOSE: To determine if individuals with CAI demonstrated greater frontal and sagittal plane movement variability in lower extremity joints compared to a control group. METHODS: Eighty-eight volunteer recreational athletes were recruited, 44 with CAI (19 Males: 20±1yrs, 76±9kg, 178±7cm; 25 Females: 20±1yrs, 64±8kg, 168±5cm) and 44 stable ankle Controls (20 Males: 19±1yrs, 73±8kg, 178±7cm; 24 Females: 20±1yrs, 61±8kg, 166±5cm). CAI participants had a history of moderate-severe ankle sprain, ≥2 episodes of instability in the last year, and reported decreased ankle joint function on the Cumberland Ankle Instability Tool. Control participants had a history of ≤1 mild-moderate ankle sprain and no episodes of instability. After measuring maximum vertical jump height, participants performed 10 single leg anterior jumps at 50% max height. Ankle, knee, and hip motion in 3 planes were measured using a 7-camera infrared tracking system (240Hz) synchronized with a force platform (1200Hz). Trials were normalized to 100% for a 1 second period after initial foot contact, and average ensemble curves of 10 trials were created for the landing leg. The coefficient of variation (CV) of the ensemble curve of each variable was calculated. Due to data violating assumptions of normality, loge (ln) transformation was performed. Independent samples t-tests were utilized with a=0.05. RESULTS: The CAI group demonstrated significantly lower CVln values for hip sagittal (3.6±0.4) motion than Controls (4.0±1.0) (p=0.02). The CAI group also demonstrated lower CVln values for hip frontal plane motion (3.8±0.5) than Controls (4.3±1.0) (p=0.007). CONCLUSIONS: Individuals with CAI demonstrated less hip sagittal and frontal plane variability than Controls during an anterior single leg jump landing. Decreased variability at only the proximal joint may indicate central sensorimotor changes in individuals with CAI and a decreased ability to adapt quickly to external perturbations. Supported by University of Georgia Research Foundation.