Maximal lateral ligament strain and loading during functional activities: Model-based insights for ankle sprain prevention and rehabilitation

BACKGROUND: Although it is generally accepted that sports activities present a high risk of lateral ligament injury, the extent to which ligaments are loaded during functional activities is less explored. This is relevant when considering ankle sprain prevention and staged rehabilitation following ligament sprain or reinforcing surgery. Therefore, anterior talofibular ligament, calcaneofibular ligament and posterior talofibular ligament strain and loading were evaluated, based on a newly developed loading index, during movements executed during daily life and rehabilitation. METHODS: Three-dimensional motion analysis data was acquired in 10 healthy volunteers during eleven different movements and processed using musculoskeletal modelling. Maximal lateral ligament strain and ligament loading, based on an new index accounting for the ankle and subtalar moment magnitude, ligament strain magnitude and duration, were calculated and statistically compared to ligament strain and loading during walking and a reference clinical (talar tilt) test. FINDINGS: Anterior talofibular, calcaneofibular and posterior talofibular lateral ligament loading were highest during vertical drop jumps, medio-lateral single leg hops and running. Additionally, anterior talofibular loading was high during stair descending, calcaneofibular loading during single leg stance without visual feedback and posterior talofibular loading during anterior single leg hops. During the clinical test, anterior talofibular and calcaneofibular ligament strain were substantially lower than the maximal strain during different movements. INTERPRETATION: Our results allow classification of exercises according to the ligament loading index and maximal strain, thereby providing objective data to progressively stage ligament loading during rehabilitation.