Abnormal tibiofemoral kinematics following ACL reconstruction are associated with early cartilage matrix degeneration measured by MRI T1rho

PurposeAltered kinematics following ACL-reconstruction may be a cause of post-traumatic osteoarthritis. T1ρ MRI is a technique that detects early cartilage matrix degeneration. Our study aimed to evaluate kinematics following ACL-reconstruction, cartilage health (using T1ρ MRI), and assess whether altered kinematics following ACL-reconstruction are associated with early cartilage degeneration.MethodsEleven patients (average age: 33 ± 9 years) underwent 3 T MRI 18 ± 5 months following ACL-reconstruction. Images were obtained at extension and 30° flexion under simulated loading (125 N). Tibial rotation (TR) and anterior tibial translation (ATT) between flexion and extension, and T1ρ relaxation times of the knee cartilage were analyzed. Cartilage was divided into five compartments: medial and lateral femoral condyles (MFC/LFC), medial and lateral tibias (MT/LT), and patella. A sub-analysis of the femoral weight-bearing (wb) regions was also performed. Patients were categorized as having “abnormal” or “restored” ATT and TR, and T1ρ percentage increase was compared between these two groups of patients.ResultsAs a group, there were no significant differences between ACL-reconstructed and contralateral knee kinematics, however, there were individual variations. T1ρ relaxation times of the MFC and MFC-wb region were elevated (p ≤ 0.05) in the ACL-reconstructed knees compared to the uninjured contralateral knees. There were increases (p ≤ 0.05) in the MFC-wb, MT, patella and overall average cartilage T1ρ values of the “abnormal” ATT group compared to “restored” ATT group. The percentage increase in the T1ρ relaxation time in the MFC-wb cartilage approached significance (p = 0.08) in the “abnormal” versus “restored” TR patients.ConclusionsAbnormal kinematics following ACL-reconstruction appear to lead to cartilage degeneration, particularly in the medial compartment.