INTRODUCTION Anterior cruciate ligament (ACL) injury affects the stability and kinematics of the knee not only in the anteroposterior direction but also in the other two directions. Previous in vitro study suggested that two-bundle reconstruction was needed to resist external knee internal rotation (IR) and valgus torques [1]. However, the potential rotary instability of the knee in the coronal and transverse planes during level walking in subjects with ACL reconstruction (ACLR) using bone-patellar tendon-bone (BTB) graft, a widespread-used one-bundle technique, has not been documented. This study aimed to provide such data. METHODS Seventeen ACL-deficient (ACLD), twenty ACLR subjects using BTB graft, and ten normal subjects walked in a gait laboratory while the movement trajectories of each of the lower limb segments were measured using a motion analysis system (VICON, Oxford Metrics, U.K.). Three-dimensional peak joint angles of the affected knees were calculated and compared between groups. RESULTS There was no significant difference in the peak flexion/extension angles between the three groups. However, internal rotation (IR) angles at the ACLD knees were significantly larger than those at the normal and ACLR knees. The peak abduction angles at the ACLD knees tended to be larger than normal (p=0.053) and were significantly larger than those of the ACLR knees. DISCUSSION AND CONCLUSION The results suggest that ACLD knees may have greater abduction and IR instability during walking whereas one-bundle ACL reconstruction seems to lead to a close-to-normal abduction and IR stability. The stability of the knee during more strenuous activities and its longitudinal changes require further study.
