Chronic Pain Severity Modifies Gait Biomechanics and Muscle Activation in Individuals with Chronic Ankle Instability

To investigate differences in neuromechanics during walking between individuals with chronic ankle instability (CAI) reporting high and low chronic pain, and healthy controls, with a focus on stance-phase joint kinematics and muscle activation patterns.

Sixty physically active participants were classified into three groups: CAI with high pain (n=20), CAI with low pain (n=20), and controls (n=20). Pain severity was determined using the Foot and Ankle Outcome Score pain subscale. Three-dimensional lower extremity kinematics and surface electromyography activation of six lower extremity muscles were recorded during overground walking at self-selected speed. Functional data analysis was used to identify stance-phase differences between groups.

Relative to controls, both CAI groups exhibited reduced activation of the peroneus longus and gluteal muscles across multiple stance subphases, with more widespread reductions in the high pain group-particularly diminished tibialis anterior (0-15%), gluteus medius (15-45%), and gluteus maximus (0-20%, 30-50%). Compared with the low pain group, the high pain group demonstrated greater ankle dorsiflexion during midstance (20-45%), greater knee flexion in early stance (5-15%) and preswing (85-95%), and greater hip flexion throughout early stance (0-20%). Increased hip adduction occurred in midstance (30-50%).

Individuals with CAI who report greater pain severity demonstrate distinct, time-specific gait deviations and greater neuromuscular inhibition, which may extend beyond the effects of instability alone. These findings highlight the potential role of pain in influencing gait adaptations in chronic ankle instability and underscore the importance of considering pain in the evaluation and rehabilitation of these individuals.