Proximal-dominant knee-ankle coordination compensations in football players with chronic ankle instability under high...

Chronic ankle instability (CAI) is associated with alterations in lower limb biomechanics. However, little is known about the knee-ankle joint coordination characteristics in individuals with CAI. This study aimed to investigate sagittal plane kinematic differences and knee-ankle coordination strategies in football players with CAI under different locomotor load conditions.

Forty male football players (CAI: n = 20; control: n = 20) completed low-load (walking: mean 3.76 km/h, 3.2-4.8 km/h) and high-load (running: mean 14.33 km/h, 12.2-16.8 km/h) treadmill tasks. A 3D motion capture system was used to record knee and ankle kinematics. Statistical Parametric Mapping (SPM) was used to analyse group and speed effects. Vector coding (VC) was applied to quantify knee-ankle coordination patterns, categorised into four coupling modes.

Compared with healthy controls, participants with CAI showed significantly reduced ankle dorsiflexion during running at 22%-42% (p < 0.001, -4.9° to -11.3°) and 75%-100% (p < 0.001, -5.2° to -7.0%) of the gait cycle. Knee flexion was significantly reduced across the entire running cycle (0%-100%, p < 0.001, -12.3° to -33.4°). VC analysis revealed particularly transitions toward proximal-dominant strategies, such as at 43%-46% (p < 0.001, Δ = 154.46°) and 62%-63% (p = 0.008, Δ = 9.39°), indicating increased reliance on knee control. Moreover, at 47%-49%, a rigid coupling state was maintained (p = 0.003, Δ = 170.19°), while 69%-75% of the gait cycle saw a reemergence of distal-dominant control during swing (p = 0.025- < 0.001, Δ = 24.06°-48.45°). Note: Δ refers to the mean difference between groups.

This study revealed significant differences in knee-ankle joint coordination between CAI patients and healthy controls. The findings suggest that CAI-related motor control adaptations are load-dependent and follow a distal-to-proximal compensatory strategy. These results highlight the importance of incorporating inter-joint coordination retraining into rehabilitation, particularly under high-load locomotor scenarios.

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