Alterations of kinetic characteristics in step up and over test in patients with anterior cruciate ligament deficiency.

The purpose of this study is to investigate the alterations of kinetic characteristics in the step up/over test in patients with acute and chronic anterior cruciate ligament (ACL) deficiency. Twenty acute, twenty chronic ACL-deficient (ACLD) patients, and forty healthy controls participated in this study. The step up/over test was performed on a clinical force platform system to obtain the following variables: movement time, lift-up index and impact index. The percentages of the indexes from the stepping leg and time of step-up and swing- over were further calculated. These variables were examined statistically by using mixed repeated measure analysis of variance to reveal the differences between groups and between limbs. Smaller lift-up forces and longer swing-over time in both ACLD groups than those in the control group were found. One exception was the lift-up index in the affected side condition of the acute ACLD group, which was not significantly different from the controls. A reduced contribution to the impact index from the affected stepping leg was also found in the acute ACLD group. The acute ACLD group showed no significant change in their step-up strategy at the affected limbs, but they may have a poorer eccentric control of the affected knees on the step and thus put a larger portion of loading onto the unaffected landing leg. Our results indicated the lift-up index, swing-over time and load- distributing strategy at impact may be important parameters in monitoring functional recovery in patients with ACL deficiency. The detected alterations in these parameters could be used as a reference to design proper rehabilitation exercises for these patients. Key pointsThe lift-up index and the time of swing-over could be important parameters for indentifying functional impairments in patients with ACL deficiency.The differences between limbs were found only in the acute ACLD group with a larger lift-up index and smaller load-distribution at impact on the affected limb.The step up/over test on the clinical force platform system could be helpful in providing a reference to design proper rehabilitation exercise and to monitor the recovery of the functional ability in patients with ACL deficiency.