Toe-out landing reduces anterior talofibular ligament strain while maintains calcaneofibular ligament strain in people with chronic ankle instability

Background: The anterior talofibular ligament (ATFL) and the calcaneofibular ligament (CFL) are vulnerable to be torn or ruptured during lateral ankle sprain (LAS), especially in people with chronic ankle instability (CAI). This study aims to determine whether landing with a larger toe-out angle would influence the ATFL and CFL strains in people with CAI, aiming to contribute to the development of effective landing strategies to reduce LAS risk.

Methods: Thirty participants with CAI (22 males and 8 females, age: 21.6 ± 1.5 years, height: 175.3 ± 7.1 cm, body mass: 70.8 ± 7.1 kg) were recruited. Each participant landed on a specialized trap-door device, with their unaffected limbs on a support platform and their affected limbs on a moveable platform, which could be flipped 24° inward and 15° forward to mimic LAS condition. Two landing conditions were tested, i.e., natural landing (NL, with natural toe-out angle at landing) and toe-out landing (TL, with increased toe-out angle to over 150% of that under the NL conditions). Kinematic data were captured using a twelve-camera motion analysis system, and the ATFL and CFL strains were calculated using a three-dimensional rigid-body foot model. Paired sample t-tests and Pearson's correlations were used to analyze data.

Results: Compared to NL conditions, the ATFL strain decreased (p < 0.001, d = 2.42), while the CFL strain remained unchanged (p = 0.229, d = 0.09) under TL conditions. The toe-out angle was negatively and strongly correlated with the ATFL strain (r = -0.743, p < 0.001) but not with the CFL strain (r = 0.153, p = 0.251). Compared to NL conditions, participants exhibit a lower ankle inversion angle (p < 0.001, d = 0.494), a higher plantarflexion angle (p < 0.001, d = 1.101), and no significant difference in external rotation angle (p = 0.571, d = 0.133, Fig. 5) under TL conditions.

Conclusion: Toe-out landing may reduce the ATFL strain while maintaining the CFL strain in people with CAI, thereby reducing the risk of LAS.