Abstract: BACKGROUND: One of the main goals after anterior cruciate ligament reconstruction is to restore normal gait patterns. However, to date, a limited number of studies have examined changes in gait asymmetry after anterior cruciate ligament reconstruction.
OBJECTIVE: To explore asymmetric changes in knee kinematics and dynamics under different stride length conditions.
METHODS: Thirty subjects (15 males and 15 females) 3 months after anterior cruciate ligament reconstruction of the single knee were included in this study. Among them, each subject received the walking test with three different stride lengths, a normal stride length and a 30% as well as a 50% increase in the normal stride length. Knee kinematic and kinetic indices were collected by means of an Italian BTS infrared motion capture system and a dynamometer table, where kinematic indices included knee flexion, extension, and adduction angles, and kinetic indices included ground reaction forces, knee flexion moments, knee extension moments, and knee adduction moments. The asymmetry index values of the kinematic and kinetic indices were calculated. A one-way analysis of variance was used to compare the differences in asymmetry of each parameter under different stride length conditions.
RESULTS AND CONCLUSION: (1) Compared with the asymmetry indices of normal step length, the indices of knee flexion angle, knee flexion moments, knee adduction moments, knee extension moments, and ground reaction forces were significantly lower when the step length was increased by 30% (P < 0.05); the indices of knee adduction angle, knee flexion angle, knee extension angle, knee adduction moments, knee extension moments, knee flexion moments, and ground reaction forces were significantly lower when the step length was increased by 50% (P < 0.05). (2) When the step length was increased by 50%, the indexes of knee adduction angle, knee extension moments, and ground reaction forces were significantly lower than when the step length was increased by 30% (P < 0.05). (3) These findings suggest that increasing stride length improves gait asymmetry after anterior cruciate ligament reconstruction, but an increase of 50% is superior, which in turn relieves the loads placed on the anterior cruciate ligament during walking. Meanwhile, step length can be used as an adjustable variable in gait to prevent and relieve symptoms of pain, improve knee function, and enhance quality of life in patients with post-anterior cruciate ligament reconstruction injuries in future clinical work.

Key words: anterior cruciate ligament reconstruction, stride length, kinematics, dynamics, asymmetry, walking test, one-way analysis of variance