Six degrees-of-freedom kinematics of ACL deficient knees during locomotion—compensatory mechanism

The purpose of the study was to investigate six degrees-of-freedom (DOF) kinematic changes in anterior cruciate ligament ACL-deficient knees during locomotion and the possible compensatory mechanism involved. Compared with healthy subjects, ACL-deficient patients walked with increased tibial external rotation throughout most of the stride and increased tibial abduction at the heel contact, and the tibia was more anterior during swing phase (P<0.05). Considering tibial external rotation and abduction unload the ACL, the kinematic changes indicated compensatory mechanism developed by patients to avoid unstable knee positions due to the loss of the ACL or to avoid stretching a partially torn ACL.