Unexpected inversion perturbation during a single-leg landing in patients with chronic ankle instability

It remains unclear how unexpected perturbations during single-leg landings affect lower extremity kinematics and muscle activations in patients with chronic ankle instability (CAI). The purpose of this study was to identify the differences in lower extremity movement patterns among CAI subjects, copers, and healthy controls. Sixty-six people including 22 CAI subjects, 22 copers, and 22 healthy controls volunteered to participate in the study. Lower extremity joint kinematics and EMG activations from 200-ms pre to 200-ms post the initial contact during unexpected tilted landings were measured. Functional data analysis was used to evaluate between-group differences for outcome measures. Relative to copers and healthy controls, CAI subjects showed more inversion from 40-ms to 200-ms after initial contact. Relative to healthy controls, CAI subjects and copers showed more dorsiflexion. Relative to healthy controls, CAI subjects and copers showed more muscle activation in tibialis anterior and peroneus longus, respectively. In conclusion, CAI subjects demonstrated greater inversion angles and muscle activation before initial contact compared to LAS copers and healthy controls. This suggests that CAI subjects and copers prepare for their landing with protective movements, but the prepared movements shown by CAI subjects may be insufficient to reduce risk of recurrent injury.