MRI-Histopathology Correlation of Cartilage and Bone in Early Knee Osteoarthritis

The study aimed to investigate the correlation between advanced magnetic resonance imaging (MRI) parameters of articular cartilage and subchondral bone with histopathological changes in patients with early knee osteoarthritis (OA), to assess the utility of MRI in detecting early degenerative changes.

A prospective observational study was conducted in 40 patients aged 40-65 years with clinical and radiographic evidence of early knee OA (Kellgren-Lawrence grade I-II). All patients underwent 3.0 Tesla MRI, including morphological sequences, T2 mapping, and T1ρ mapping, to evaluate cartilage integrity and subchondral bone lesions. Cartilage and subchondral bone samples were obtained during arthroscopy or planned surgical procedures and analyzed histologically using Hematoxylin and Eosin and Safranin-O/Fast Green staining. Cartilage degeneration was graded using the Mankin scoring system, and subchondral bone changes were assessed for marrow edema, trabecular remodeling, and fibrosis. MRI parameters were correlated with histopathological scores, and statistical analysis was performed using Pearson's/Spearman's correlation and Cohen's kappa statistics.

MRI detected early cartilage degeneration, predominantly in the medial femoral condyle and tibial plateau, with elevated T2 (42.8 ±6.2 ms) and T1ρ (48.6 ± 7.1 ms) values in affected regions. Histopathology revealed early degenerative changes with mean Mankin scores of 4.2 ± 1.5 and subchondral bone alterations, including marrow edema (40%), trabecular remodeling (30%), and fibrosis (25%). A strong positive correlation was observed between T2/T1ρ relaxation times and Mankin scores (r = 0.72 and r = 0.69, respectively; P < 0.001). Semiquantitative MRI assessment of bone marrow lesions showed moderate agreement with histopathology (Cohen's kappa = 0.61).

Advanced MRI techniques, including T2 and T1ρ mapping, accurately reflect early cartilage degeneration and show moderate correlation with subchondral bone changes. These findings support the use of MRI as a non-invasive diagnostic tool for early detection and assessment of knee OA, particularly in the medial compartment. However, the findings should be interpreted with caution due to the small sample size and the cross-sectional design of the study.