Neuromechanical Patterns Underlying Chronic Ankle Instability

Abstract

Lateral ankle sprain is one of the most common musculoskeletal injuries among physically active populations. Chronic ankle instability (CAI) can develop following a substantial ankle sprain and has a high prevalence rate. CAI is a complex and multifactorial condition arising from a range of neuromechanical impairments. However, the contributing factors to the development of CAI are poorly understood due to conflicting results of the previous research influenced by the variations in movement tasks and definitions of the CAI condition, and limited evidence on the dynamic interaction between lower limb neuromechanical parameters during functional activities. This thesis aimed to identify lower limb biomechanical alterations during dynamic tasks and to explore the neuromuscular components of peroneal muscles in individuals with CAI compared to a healthy control group.

Three experimental studies with thirty-two participants (17 CAI and 15 controls) were conducted to identify lower limb biomechanical alterations associated with CAI. Sagittal and frontal plane ankle and hip joint angles and moments, and mediolateral foot balance (MLFB) were calculated during walking, running and lateral jump-landing tasks. In addition, a systematic review with meta-analysis has been carried out to synthesise research on neuromuscular characteristics of peroneal muscles, including corticospinal excitability, strength, proprioception (force sense) and electromyographic measures in individuals with CAI compared to healthy controls.

During the walking task, no significant between-group differences were observed for the research variables including ankle kinematics, ankle and hip moments, and MLFB. During the running, the individuals with CAI exhibited a significantly greater peak plantar flexion angle (p = 0.022) during early stance, lower plantar flexor moment (p < 0.001) including a reduced peak plantar flexor moment (p = 0.002), as well as more laterally deviated MLFB (p = 0.014) than the control group throughout the midstance phase.

Hip moments were not significantly different between the groups during the running task. In the jump-landing, the CAI group demonstrated a greater peak hip adduction angle (p = 0.039) and greater hip extensor moment (p = 0.008) in the early phase of the ground contact compared to the control group. No intergroup differences were found in ankle joint kinematics or moments, or in MLFB during the jump-landing task. Among 13,670 studies retrieved, 42 were included in the systematic review, with 25 eligible for meta-analysis, revealing significantly less isometric evertor force sense accuracy and prolonged peroneus longus latency during single leg landing inversion perturbation test under unexpected conditions in individuals with CAI than the control group.

These findings may suggest potential neuromechanical dysfunctions in the sensorimotor system underlying the mechanisms that characterise CAI, providing insight into the complexity and multifaceted nature of the issue and helping to inform the optimisation of future intervention designs.