Three-dimensional ankle kinematics of the full gait cycle in patients with chronic ankle instability: A case-control study

Objectives: The ankle kinematic characteristics of chronic ankle instability (CAI) at different gait phases and dimensions were not directly and overall explained. These characteristics have yet to be established. This study aimed to observe ankle kinematic changes of CAI, and explore their mechanisms, at different gait phases and dimensions in full gait cycle. Methods: A three-dimensional (3D) motion capture system measured the 3D ankle movements of 53 individuals with CAI (meanage = 25.11 +/- 6.01years, meanheight = 170.77 +/- 7.80 cm, mean-mass = 64.28 +/- 9.28 kg) and 53 healthy controls (meanage = 24.66 +/- 6.32 years, meanheight = 169.98 +/- 9.00 cm, meanmass = 63.11 +/- 9.62 kg) during barefoot walking overground at a self-selected speed. Once the acquisition results were processed with visual 3D software, the kine-matics data were exported, and the eight phases of the gait cycle were identified. Results: As compared with the control group, individuals with CAI displayed a significantly smaller plantarflexion in toe off (P = 0.049, Cohen's d = 0.387), a significantly increased inversion in heel strike (P = 0.007, Cohen's d = 0.271) and initial swing (P = 0.035, Cohen's d = 0.233), mid-swing (P = 0.019, Cohen's d = 0.232) and end-swing (P = 0.021, Cohen's d = 0.214), and significantly smaller eversion in mid stance(P = 0.010, Cohen's d = 0.288)and heel off (P = 0.033, Cohen's d = 0.089). Significant between-group differences in ankle kinematics were observed in the sagittal and frontal planes, but not in the horizontal plane, during walking. Conclusion: When walking, patients with CAI have altered sagittal-and frontal-plane kinematics during different stance and swing phases. These kinematic changes require multi-dimensional, dynamic, continuous functional assessment and specialized rehabilitation intervention.