Background: High risk of cartilage degeneration and premature osteoarthritis development has been clinically observed in anterior cruciate ligament (ACL) deficient knees. The risk has not been significantly reduced even after ACL reconstructive surgery. It was hypothesized that three-dimensional knee joint kinematics has been altered after ACL injury, and the biomechanical alteration has not been fully restored to a normal level after reconstructive surgery.
Methods: Spatiotemporal parameters and three-dimensional knee joint rotations and translations were measured in ACL-deficient, ACL-reconstructed, and ACL-intact knees during level walking. The variables were compared between the ACL-deficient and ACL-intact knees, as well as between the ACL-reconstructed and ACL-intact knees.
Findings: Altered spatiotemporal variables and key event timings in a gait cycle were observed in both ACL-deficient and ACL-reconstructed subjects. Significant reduction of extension was observed in the ACL-deficient knees during midstance and in the ACL-reconstructed knees during swing phase. Greater varus and internal tibial rotation were identified in the ACL-deficient knees. Although being small in magnitude, these secondary kinematic alterations were consistent throughout the whole gait cycle, and such trends were not eliminated in the ACL-reconstructed knees.
Interpretation: Significant abnormalities of spatiotemporal performance and three-dimensional joint kinematics during walking were identified in the ACL-deficient knees. The ACL-reconstructed knees exhibited some improvement in joint kinematics, but not being fully restored to a normal level. Identification of biomechanical alterations during daily activities in ACL-deficient and ACL-reconstructed knees could help better understand clinical outcomes and seek improvement in surgical technique and rehabilitation regimen for ACL injury treatment.