Lower limb landing biomechanics in subjects with chronic ankle instability.

PURPOSE The literature on lower limb kinematic deviations in subjects with chronic ankle instability (CAI) during landing tasks is limited and not consistent. Several studies only report joint angles at defined events rather than considering the whole kinematic curve, which might obscure possibly relevant information. Therefore, the main goal of this study was to evaluate landing kinematics of the lower limb in subjects with CAI using curve analysis. METHODS Lower limb kinematics of 56 subjects (28 subjects with self-reported CAI and 28 matched healthy controls) were measured during a barefoot forward and side jump protocol. Kinematic data were collected in a laboratory setting using an eight-camera optoelectronic system. Ground reaction forces were registered by means of a force plate built into the landing zone. After completion of each task, difficulty level and subjective stability at the ankle joint were documented using a visual analog scale. To compare between groups, statistical parametric mapping was used to assess group differences between mean joint angles over the entire impact phase. RESULTS SPM analysis of kinematic curves of the hip, knee, and ankle showed no significant differences between the subjects with CAI and the control group independent of jump direction. Subjects with CAI did report higher feelings of instability for both landing tasks and a higher difficulty level for the forward jump. CONCLUSIONS Our results showed no altered lower limb kinematics in subjects with CAI compared to a healthy control group during a forward and side jump landing task. Therefore, these results question the hypothesis of kinematic deviations as part of an underlying mechanism of CAI.