Foot and Shank Coordination During Walking in Copers Compared With Patients With Chronic Ankle Instability and Controls

BACKGROUND: Chronic ankle instability (CAI) alters sensorimotor function and joint coordination, but ankle coordination during walking in copers (patients with a history of ankle sprain without any residual symptoms of CAI) remains unknown. PURPOSE: To identify foot and shank coordination patterns that discriminate among individuals with CAI, copers, and healthy controls and to investigate whether copers display a different strategy to overcome altered sensorimotor function after a lateral ankle sprain compared with individuals with CAI and healthy controls. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 51 participants (17 participants with CAI, 17 copers, 17 healthy controls) walked on an instrumented treadmill at a fixed speed of 1.20 m/s for a 10-second trial, from which 8 consecutive gait cycles were extracted for analysis. Heel strike and toe-off were identified for each stance phase, and each stance phase was normalized to 100 time frames. A curve analysis was performed to detect group mean differences in vector coding coupling angles and coordination variabilities for sagittal plane ankle motion/transverse plane tibial plane motion (SAK/TT) and frontal plane ankle motion/transverse plane tibial motion (FAK/TT) with 90% CIs. RESULTS: During the terminal stance, CAI and coper groups demonstrated an inversion–tibial external rotation coupling, while controls displayed a dorsiflexion–tibial internal rotation strategy. During midstance, there were no differences between the coper, CAI, or control groups. At 0% to 20% of stance, the CAI group showed the most variability, while copers showed the least. During midstance, both copers and controls displayed an increase in variability earlier than the CAI group. The CAI group displayed a peak in variability from 39% to 43% of stance, which was greater than copers. During the propulsive phase (from heel-off to toe-off), the CAI group showed greater SAK/TT variability than both copers and controls. Similar to SAK/TT variability, the CAI group showed an earlier peak in FAK/TT variability compared with controls. CONCLUSION: The CAI, coper, and control groups displayed different ankle joint coupling patterns and coordination variability during a walking gait cycle. CLINICAL RELEVANCE: Copers may have the ability to alter their coordination during walking, which may help us understand the underlying mechanism of CAI.