Anterior translation and rotational stability of anterior cruciate ligament-deficient knees during walking: speed and turning direction.

BACKGROUND: Anterior cruciate ligament (ACL) rupture is one of the most common injuries associated with the knee. After ACL injury, knee joint stability can be altered, resulting in abnormal loading during functional activities. Since ACL-deficient (ACLD) knees are also vulnerable to translational and rotational instability, patients need to be wary of certain motions encountered in daily life. The present study investigated the effect of walking speed and pivoting directional change during gait on knee joint kinematics of ACLD knees. We hypothesized that faster walking and crossover turning would induce severe kinematic changes.

METHODS: Thirty-five patients (22 males and 13 females) having a unilateral isolated subacute ACLD knee (from 1 to 3 months after injury) and contralateral intact (CLI) knee participated in this study. Spatiotemporal parameters, three-dimensional (3D) knee joint angles, and anterior-posterior (AP) translation were obtained by a 3D high-speed motion-capturing system. The CLI knee of each patient served as the control. The calculated AP stability and knee joint angles were used to test the research hypothesis. Mixed two-way repeated measures analysis of variance was performed to clarify the effects of walking speed and pivoting direction with a significance of 0.05. When a significance of mean comparison was detected, a post hoc test was performed.

RESULTS: Significant and consistent increased AP translation of the tibia relative to the femur at the whole stance phase of the gait cycle was evident in ACLD knees compared to CLI knees for normal and faster (20 % greater than normal) walking speeds. Faster walking speed did not induce significantly more anterior location of the tibia. In addition, ACLD knees were significantly less extended than CLI knees during a large portion of midstance. Although there was a consistent varus offset between the curves of ACLD and CLI knees, the difference did not reach statistical significance during the stance phase. Also, ACLD knees did not show any significant difference in tibial rotation compared to CLI knees during the entire stance phase of the gait cycle. For pivoting turns, ACLD knees showed significantly less extended and varus offset than CLI knees only during the cutting turn. ACLD knees exhibited less tibial internal rotation during the crossover turn and less tibial external rotation during the cutting turn than CLI knees.

CONCLUSIONS: In ACLD knees, the tibia tended to shift more anteriorly and changed with less extension at walking. However, faster walking speed did not induce any significant difference compared with normal-speed walking. In addition, ACLD knees displayed kinematic changes during pivoting, but not the crossover turn.