Abnormal tibial position is correlated to early degenerative changes one year following ACL reconstruction

Altered knee kinematics following ACL reconstruction may predispose patients to the development of early onset post-traumatic osteoarthritis. The goal of our study was to examine the longitudinal interrelationship between altered tibial position relative to the femur and cartilage health measured by quantitative T1ρ MRI. Twenty-five patients with isolated unilateral ACL injury underwent kinematic and cartilage T1ρ MRI at baseline prior to ACL reconstruction and then at 1-year post-reconstruction. Tibial position relative to the femur in the anterior-posterior plane was calculated as well as cartilage T1ρ relaxation values in the injured and uninjured knee. At baseline prior to ACL reconstruction, the tibia was in a significantly more anterior position relative to the femur in the ACL deficient knee compared to the healthy contralateral knee. This difference was no longer present at 1-year follow-up. Additionally, the side-side difference in tibial position correlated to increased cartilage T1ρ relaxation values in the medial compartment of the knee 1-year post-reconstruction. Altered tibial position following ACL reconstruction is correlated with detectable cartilage degeneration as soon as 1 year following ACL reconstruction.