# Proximal‐dominant knee–ankle coordination compensations in football players with chronic ankle instability under high load

## TL;DR

Football players with chronic ankle instability show altered knee-ankle coordination during running, relying more on knee movement to compensate for ankle issues.

## Contribution

The study reveals load-dependent compensatory strategies in knee-ankle coordination among CAI patients during high-speed locomotion.

## Key findings

- CAI participants showed reduced ankle dorsiflexion and knee flexion during running compared to controls.
- Vector coding analysis revealed proximal-dominant coordination strategies in CAI patients at specific gait cycle phases.
- Load-dependent compensatory strategies suggest a distal-to-proximal shift in motor control under high locomotor loads.

## Abstract

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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Load‐dependent alterations in knee–ankle coordination in football players with chronic ankle instability: This summarises a study investigating how chronic ankle instability (CAI) affects sagittal plane kinematics and knee–ankle coordination strategies under different loading conditions (walking and running) in male football players. A total of 40 participants (20 CAI, 20 control) completed treadmill‐based gait assessments, and three‐dimensional motion capture was used to record joint angles. Statistical parametric mapping (SPM) and vector coding (VC) analyses were employed to identify joint‐level and inter‐joint coordination differences.