Greater Ankle Laxity and Smaller Evertor Muscles in Conjunction are Linked to Symptoms of Chronic Ankle Instability in Collegiate Basketball Athletes

Purpose: Investigate the combined effects of ankle joint laxity and evertor muscle size on symptoms of chronic ankle instability (CAI) using both quantitative imaging and clinical gradings of laxity. We also aimed to establish the relationship between quantitative and clinical measures of laxity. Methods: Division-I basketball athletes underwent preseason magnetic resonance imaging to quantify evertor muscle volumes and completed the Cumberland Ankle Instability Tool (CAIT). Laxity, defined as maximum talofibular displacement, was measured during a reverse anterolateral drawer test (RALD) using Bmode ultrasound and an opticalflow bonetracking algorithm. Clinical RALD gradings (positive/negative) were assigned by the physical therapist performing the test. Linear mixedeffects models evaluated (1) the effects of displacement, evertor muscle volume, and their interaction on CAIT scores, adjusting for sex, and (2) the association between clinical RALD grade and maximum displacement. Results: Twentynine athletes (58 ankles) were included for the quantitative versus clinical laxity comparison; 21 athletes (36 ankles) were included for the primary analysis. Maximum displacement differed between clinical RALD grades (p < 0.01), with greater displacement in positive versus negative tests. There was a significant interaction effect between displacement and evertor muscle volume on CAIT scores (p < 0.01). Greater laxity related to worse CAIT scores, particularly in athletes with smaller evertor muscle volumes. The model using clinical RALD grade did not show significant effects on CAIT scores. Conclusions: Greater ultrasoundquantified ankle laxity was associated with more severe CAI symptoms; however, this relationship was weaker in athletes with larger evertor muscles. Ultrasoundbased measures of laxity were associated with CAI, whereas clinical gradings were not, indicating that quantitative measures of laxity may serve as a valuable metric for future research and guiding clinical care.