Background Anterior cruciate ligament (ACL) injuries occur in left leg more frequently than in right legs, but the cause for this observation is not clear. So, it is interesting to analyze the difference of causes of ACL injury between both legs.

Objective To compare the difference of left and right knee joint kinematics during a 90°direction side step cutting (SSC) maneuver. The hypothesis was that smaller maximum knee flexion and larger knee valgus in left knee.

Design Repeated measures design.

Setting Laboratory setting.

Subjects Included were 14 female collegiate basketball athletes with no orthopaedic diagnosis in the lower extremities. Their average age, height, weight and length of career as basketball athletes were 21.0 years, 160.1 cm, 54.5 kg, and 6.2 years, respectively. This study was approved by the institutional review board.

Inteventions All subjects were right dominant and kicked the ball with their right legs.

Main outcome measurements Motion of each subject during 90° SSC was recorded by a 6 high-speed (200 frames/s) CCD camera system (Ditect, Japan) and 3D analyzed with knee kinematics. Each subject performed 5 trials after sufficient practice, and the average of knee joint angle displacements were calculated. The power for each analysis of variance was not less than 0.75 if the effect size was more than 0.80.

Results The result showed a bimodal curve of peak knee valgus in both knees. Maximum flexion occurred at stop phase after initial contact of the subjects' leg on floor, and maximum valgus occurred almost simultaneously. There was no significant difference of angular displacement between both knees. However, there was a tendency that smaller maximum flexion and larger valgus were observed in left knee compared with right.

Conclusions Although there was no significant differences between right and left leg, small flexion and large valgus angle were observed in left knee.