Cartilage Damage and Bone Marrow Edema in Patellofemoral Versus Tibiofemoral Joints in Knee Osteoarthritis: An MRI-Based Comparative Study.

OBJECTIVES

This study aimed to evaluate and compare the distribution and severity of articular cartilage damage and bone marrow edema (BME) in the patellofemoral joint (PFJ) and tibiofemoral joint (TFJ) of knees with osteoarthritis (OA) using the Siemens MAGNETOM Vida MRI system (Siemens Healthineers, Erlangen, Germany) and to examine their mutual relationship across compartments.

METHODS AND MATERIALS: This cross-sectional observational study enrolled 60 patients older than 50 years with symptomatic knee OA. All patients underwent a 3.0 Tesla MRI with systematic evaluation of 10 TFJ and five PFJ locations. Articular cartilage integrity was scored on an eight-point ordinal scale (0-6) and subchondral BME on a four-point severity scale (0-3). Two blinded radiologists independently assessed images; Spearman's rank correlation coefficient evaluated associations between the studied parameters.

RESULTS

The study cohort had a mean age of 62.92±4.68 years with female predominance (61.7%; n=37). Inter-observer agreement was substantial (κ=0.84-0.91). Mean cartilage damage scores were comparable between PFJ (3.93±1.79) and TFJ (3.75±3.84; p=0.729). BME scores showed no significant compartmental difference (PFJ: 1.78±0.96; TFJ: 2.02±2.49; p=0.450). Robust positive correlations between cartilage damage and BME were identified at all assessed locations (ρ=0.726-1.000; p<0.001). The overall combined Spearman correlation was 0.924 (p<0.001). Elevated body mass index, higher Kellgren-Lawrence (KL) grade, and increased Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain scores were each significantly associated with higher values for both parameters.

CONCLUSION

Articular cartilage damage and subchondral BME demonstrate strong interdependence and equivalent compartmental distribution in knee OA, reinforcing the paradigm of OA as a whole-joint disease. MRI-based compartmental assessment provides clinically meaningful structural information beyond conventional radiography.