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Ankle Kinematics and Muscle Activity in Functional Ankle Instability

Monteleone, Bradley J. MD, PhD*,†,‡; Ronsky, Janet L. PhD*; Meeuwisse, Willem H. MD, PhD*; Zernicke, Ronald F. PhD*,§

Clinical Journal of Sport Medicine: January 2014 - Volume 24 - Issue 1 - p 62–68
doi: 10.1097/01.jsm.0000432858.86929.80
Original Research

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.

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

Setting: Clinical biomechanics laboratory.

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

Interventions: 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.

Main Outcome Measures: 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.

Corresponding Author: Bradley J. Monteleone, MD, PhD, Faculty of Medicine, School of Health and Exercise Sciences, University of British Columbia, 3333 University Way, Kelowna, BC V1V 1V6, Canada (

The authors report no conflicts of interest.

Received October 17, 2010

Accepted June 17, 2013

Copyright © 2014 Wolters Kluwer Health, Inc. All rights reserved.