Kinematics of balance controls in people with chronic ankle instability during unilateral stance on a moving platform

Abstract

Balance control deficits resulting from ankle sprains are central to chronic ankle instability (CAI) and its persistent symptoms. This study aimed to identify differences in balance control between individuals with CAI and healthy controls (HC) using challenging single-leg balance tasks. Twenty-three CAI and 23 HC participants performed balance tasks on a force plate that either remained static or moved mediolaterally. Force and kinematic data were recorded to measure balance and joint movements. The CAI group showed significantly shorter time-to-boundary during static conditions but no significant differences during moving conditions compared to HC. During moving conditions, CAIs exhibited greater proximal compensations, with greater range of motion and higher angular velocity in the knee, hip, and torso. while no significant differences were observed in these parameters during static conditions. Principal component analysis indicated specific kinetic chain in CAI during one-leg balance under both static and moving conditions compared to HC. These findings suggest an altered movement strategy in CAI, that ankle injuries impair the ability to stabilize both distal and proximal joints, and an altered kinetic chain from ankle to torso. Rehabilitation programs for CAI might benefit from considering the integration of the entire kinetic chain, addressing both distal and proximal joint dynamics to support effective recovery and prevent secondary injuries.

Keywords: Balance control; Chronic ankle instability; Kinematics; Perturbation; Postural strategy; Principal component analysis.

Fig. 1

A Standardised single-leg standing visualised through markers by motion capture and Motive software (version 2.1.1; https://optitrack.com/software/motive/). B Platform motion in 15-s: mediolateral sinusoidal at 1.6 Hz, with displacement (peak-to-peak displacement at 20 mm).

Fig. 2

Joint kinematics reconstructed from the PCS of PCV3. Posture diagram: the right panel of each plane illustrated a specific movement pattern in CAI, with arrows indicating the kinematic differences compared to HC by PVC3. The waveforms: were reconstructed by the mean of PCS in participants with CAI, HC and all participants of PCV3. Avg. average of all participants. The plots show ankle, knee, hip and torso angles across sagittal, frontal, and horizontal planes over 10 s. The definitions of the abbreviations in the graph are as follows: D.F. dorsiflexion, P.F. plantarflexion, Flex. flexion, Ext. extension, E.V.: Eversion, I.V.: Inversion, Add. adduction, Abd. abduction, Lat. lateral, Med. Medial, I.R. internal rotation, E.R. external rotation. The figure was plotted by Matlab 2022b (https://uk.mathworks.com/products/matlab.html).

Fig. 3

The correlation between the principal component score (PCS of PCV3) and the standard deviation of sway amplitude of the centre of pressure. The scatter plot displays positive correlations as indicated by the best-fit lines for CAI, HC and combined data (ALL). Both groups and the combined data showed statistically significant correlations.

Fig. 4

A revealed the range of motion (joint angle) during 10 s balance on both static and moving platform condition. The ranges of motion were calculated as the maximum angle minus the minimum angle. B The angular velocity was calculated as the time-derivative of joint angle. The root mean squared angular velocity. Data are expressed as means ± SD. The data were analysed using independent t-tests for comparisons between CAI and HC groups. The “*” symbol indicates significant differences between the two groups (*p < 0.05). P-values and effect sizes (Cohen’s d) are shown.