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BACKGROUND: Individuals with chronic ankle instability are prone to inversion ankle sprains during landing. Moderately increasing the foot toe-out angle during landing may reduce the occurrence of inversion ankle sprains, but no studies have directly demonstrated this effect. OBJECTIVE: To explore the effect of increased toe-out angle during landing on the peak inversion angle, peak angular velocity, and the time to peak inversion among individuals with and without chronic ankle instability. METHODS: A total of 60 participants were recruited for this study, including 30 individuals with chronic ankle instability and 30 without chronic ankle instability. The study utilized a simulated sprain apparatus for drop-landing tests, featuring a platform that could tilt forward by 24° and inward by 15°, thus simulating the foot position during an ankle inversion sprain. Participants were required to perform drop-landing tests under two landing conditions: natural landing and toe-out landing, with the latter involving a greater foot toe-out angle, over 150% more than the former. Kinematic data of participants were recorded using a 12-camera three-dimensional motion capture system. Data analysis was conducted using two-way repeated measures analysis of variance and Spearman correlation analysis. RESULTS AND CONCLUSION: (1) Significant main effects of condition were found for peak inversion angle during drop-landing (P < 0.001, η² p=0.270), peak inversion velocity (P=0.015, η² p=0.098), and peak inversion time (P < 0.001, η² p=0.260); a significant main effect of group was found for peak inversion velocity (P=0.029, η² p=0.080). (2) There were significant negative correlations between the foot toe-out angle at landing and the peak ankle inversion angle (P=0.021, r=-0.310; P=0.042, r=-0.278) as well as the peak inversion time (P=0.018, r=-0.312; P=0.021, r=-0.309) in both chronic ankle instability and non-chronic ankle instability groups. Moreover, a significant negative correlation was also found between the foot toe-out angle and peak inversion velocity in the chronic ankle instability group (P=0.021, r=-0.312). (3) It is indicated that increasing the foot toe-out angle at landing can reduce the peak inversion angle, peak inversion velocity, and the peak inversion time during landing in patients with chronic ankle instability and non-chronic ankle instability, thereby decreasing the risk of ankle inversion sprains. [ABSTRACT FROM AUTHOR]