Tibial and calcaneal coupling during walking in those with chronic ankle instability

Background: It is estimated that nearly 2 million individuals sprain their ankle each year in the US. A majority of these are recurrent injuries, which often results in chronic ankle instability. To better understand the cause of instability, previous research has looked at the coupling or coordination between leg and foot motion during locomotion. Research Question: Determine the coupling between the tibia and the calcaneus during the stance phase of walking in those without a history of ankle instability compared to those with either moderate or severe instability. Methods: Fifty-four individuals between the age of 18-30 years (15 males; 39 females) participated in this study. Each participant's history of ankle sprains and score on the Cumberland Ankle Instability survey was used to assign them to either a no, moderate or severe instability group. Electromagnetic sensors attached to the tibia and calcaneus recorded three-dimensional movement of their tibia and calcaneus during the stance phase of barefoot over ground walking. The kinematic data was referenced to the subject's standing position and time normalized to each subject's stance phase duration. The relative phase (RP) angle and RP variability between tibia internal/external rotation and calcaneal inversion/eversion motion was then calculated. A one-way analysis of variance test was used to determine if significant differences existed between the three groups of subjects on mean RP angle or variability. An alpha level of.05 was used to determine statistical significance. Results: A significant increase in RP angle and variability was found during the mid-stance phase of walking for those with severe ankle joint instability compared to those with moderate or no instability. Significance. The observed decreased coordination and increased coupling variability observed for those with severe ankle instability suggests either residual ligamentous damage, inadequate sensorimotor control, or both.