Biomechanical deficits in chronic ankle instability: a comparative study of landing strategies on a laterally inclined surface

Background Individuals with chronic ankle instability (CAI) exhibit altered biomechanics during landing. However, no studies have characterised the effects of varying landing heights during unilateral landings on inclined surfaces. Gaining this knowledge is essential for improving our understanding of biomechanical landing strategies in individuals with CAI, with the overarching goal of better characterising their biomechanical deficits in various sports-related contexts. The objective of this laboratory-based case-control study was to determine the differences in landing biomechanics from low and high heights on a laterally inclined surface in individuals with CAI compared to healthy controls. Methods Foot, ankle, knee, and hip angles, moments, and power of 16 participants with CAI and 16 healthy controls were collected during a unilateral drop landing on a 15 ^o laterally inclined surface from landing heights of 20 and 40 cm. Two-way ANOVAs with repeated-measures on the Height factor using statistical parametric mapping was used to determine the Group (control vs CAI), Height (20 cm and 40 cm), and Group X Height interaction effects for the kinematic and kinetic variables. Results Individuals with chronic ankle instability exhibited greater ankle inversion angles and less ankle eversion moments compared to healthy controls. When landing from a greater height, participants with and without CAI displayed greater midfoot and ankle pronation as well as knee and hip flexion. They also exhibited greater ankle plantarflexion and eversion moments, knee extension and hip flexion moments as well as greater ankle and knee power absorption at initial impact. Conclusion Our findings revealed that individuals with CAI demonstrate altered lower limb biomechanics, particularly greater ankle inversion angles and reduced ankle eversion moments, which may increase the risk of recurrent lateral ankle sprains. Our results also revealed a protective biomechanical mechanism when landing from greater heights in individuals with and without CAI.