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.