Evaluation of the lateral ankle dynamics during the stance phase of gait in individuals with and without chronic ankle instability

The purpose of this study was to compare the distance between the talus and the lateral malleolus and the ankle joint angles during the stance phase of gait between individuals with CAI and healthy adults using a synchronized US with a three-dimensional motion analysis (MA) system.

Ten feet of healthy adults (healthy group) and 10 feet of CAI group were included in the study. Using the US (Telemed, Lithuania) synchronized with MA system, we measured the distance between the talus and lateral malleolus during the stance phase of gait. Two-way split-plot analysis of variance was conducted, considering the presence or absence of CAI as an intersubject factor and the three phases of the gait cycle (early stance, middle stance, and terminal stance) as intrasubject factors. For items showing a significant interaction effect, post hoc comparisons were conducted using unpaired t-tests between groups with Bonferroni correction. Statistical significance was set at p0.05.

The distance between the talus and the lateral malleolus during gait was significantly increased in the CAI group compared with that in the control group throughout the stance phase (p0.001). The ankle dorsiflexion angle was smaller in the CAI group during the middle and terminal stance phases (p0.001). Additionally, the ankle inversion angle was greater in the CAI group than in the control group (p0.001).

In this study, the decrease in the ankle dorsiflexion angle and the increase in the inversion angle during the stance phase of gait may have significantly contributed to the increase in the distance between the talus and lateral malleolus. When the ankle dorsiflexes, the talus moves posteriorly, thereby causing the distance between the talus and lateral malleolus to shorten. Conversely, when the ankle plantarflexes, the talus moves anteriorly, increasing the distance between the talus and lateral malleolus. This important observation is based on findings from anatomical reports. In CAI, where the anterior talofibular ligament is likely damaged, both anatomical and kinematic factors are presumed to contribute to the increase in the distance between the talus and lateral malleolus.

Our findings show the application of the synchronized US and MA system in the assessment of mechanical instability in CAI group, which may be used to determine treatment efficacy.