Shank-rearfoot joint coupling with chronic ankle instability.

Area of Science:

• Biomechanics
• Motor Control
• Orthopedics

Background:

• Chronic ankle instability (CAI) is a common consequence of initial ankle sprains, characterized by persistent symptoms like ankle 'giving way'.
• Understanding the biomechanical alterations in CAI is crucial for developing effective interventions.
• Joint coupling and variability during locomotion are key indicators of lower limb function.

Purpose of the Study:

• To investigate differences in shank-rearfoot joint coupling and variability throughout the gait cycle between individuals with CAI and healthy controls.
• To compare these kinematic differences during both walking and jogging activities.
• To explore the relationship between altered joint mechanics and sensorimotor control in CAI.

Main Methods:

• Utilized a vector coding method to analyze angle-angle relationships and stride-to-stride variability (VCV) of shank-rearfoot coupling.
• Collected 3D kinematic data from 28 young adults (15 CAI, 13 controls) during treadmill walking and jogging.
• Calculated direction (θ) and magnitude of joint coupling, alongside VCV, across different phases of the gait cycle.

Main Results:

• During walking, CAI subjects showed lower θ (increased rearfoot-to-shank motion) in early and late swing, with altered magnitude patterns.
• CAI participants exhibited reduced stride-to-stride variability (lower VCV) during the stance phase of walking.
• In jogging, the CAI group consistently displayed lower θ measures during both stance and swing phases compared to controls.

Conclusions:

• Significant differences in shank-rearfoot coupling and variability exist between CAI subjects and healthy controls during walking and jogging.
• Altered joint mechanics in CAI may reflect underlying changes in sensorimotor control mechanisms.
• These biomechanical deviations could contribute to the recurrent instability experienced by individuals with CAI.