Altered ankle kinematics and shank-rear-foot coupling in those with chronic ankle instability.

CONTEXT: Kinematic patterns during gait have not been extensively studied in relation to chronic ankle instability (CAI).

OBJECTIVE: To determine whether individuals with CAI demonstrate altered ankle kinematics and shank-rear-foot coupling compared with controls during walking and jogging.

DESIGN: Case control.

SETTING: Motion-analysis laboratory.

PARTICIPANTS: 7 participants (3 men, 4 women) suffering from CAI (age 24.6 +/- 4.2 y, height 172.6 +/- 9.4 cm, mass 70.9 +/- 8.1 kg) and 7 (3 men, 4 women) healthy, matched controls (age 24.7 +/- 4.5 y, height 168.2 +/- 5.9 cm, mass 66.5 +/- 9.8 kg).

INTERVENTIONS: Subjects walked and jogged on a treadmill while 3-dimensional kinematics of the lower extremities were captured.

MAIN OUTCOME MEASURES: The positions of rear-foot inversion-eversion and shank rotation were calculated throughout the gait cycle. Continuous relative-phase angles between these segments were calculated to assess coupling.

RESULTS: The CAI group demonstrated more rear-foot inversion and shank external rotation during walking and jogging. There were differences between groups in shank-rear-foot coupling during terminal swing at both speeds.

CONCLUSIONS: Altered ankle kinematics and joint coupling during the terminal-swing phase of gait may predispose a population with CAI to ankle-inversion injuries. Less coordinated movement during gait may be an indication of altered neuromuscular recruitment of the musculature surrounding the ankle as the foot is being positioned for initial contact.