Ankle kinematics and muscle activity in functional ankle instability.
OBJECTIVE
Following an ankle injury, many patients have functional ankle instability (FAI) with an increased predisposition to reinjury. The purpose of this study was to assess the effects of FAI on ankle kinematics and muscle activity during a lateral hop movement.


METHODS
Cross-sectional and observational study; all data collection for each subject was performed on 1 day.


METHODS
Clinical biomechanics laboratory.


METHODS
Two groups were studied: (1) Control group-no ankle injury (n = 12), and (2) FAI group (n = 12).


METHODS
The lateral hop movement consisted of multiple lateral and medial 1-legged hops over an obstacle (width, 72.5 cm; depth, 25.5 cm; height, 14.3 cm) onto adjacent force platforms. Each subject was instructed to perform as many lateral hops as possible during the 6-second trial. Means, SDs, 95% confidence intervals of the differences, and P-values were calculated.


METHODS
Ankle kinematics and muscle activity throughout the lateral hop movement.


RESULTS
Significant differences existed between groups for mean (SD) dorsiflexion ankle positions--FAI 82.4 degrees (6.4) versus normal 75.2 degrees (10.1) and tibialis anterior normalized muscle activity--FAI 0.27 (0.21) versus normal 0.16 (0.13) at ground contact.


CONCLUSIONS
The FAI group revealed greater tibialis anterior muscle activity and dorsiflexion ankle position at contact moving in the lateral direction. These differences between groups may have been related to an inherent predisposition to ankle injuries, a preexisting difference in task performance, a consequence of injuries, or a compensatory adaptation to previous injuries.
*McCaig Center for Joint Injury and Arthritis Research, University of Calgary, Calgary, Alberta, Canada; †LifeMark Health Sport Medicine Centre, Kelowna, British Columbia, Canada; ‡Faculty of Medicine, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada; and §Departments of Orthopaedic Surgery and Biomedical Engineering and School of Kinesiology, University of Michigan, Ann Arbor, Michigan.
Bradley J
BJ
Monteleone
Janet L
JL
Ronsky
Willem H
WH
Meeuwisse
Ronald F
RF
Zernicke
D000328:Adult; D016512:Ankle Injuries / Q000503:physiopathology*; D000843:Ankle Joint / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology*; D055815:Young Adult