Dynamic CT–Based Quantification of Patellofemoral Contact Area Following Cartilage Removal: An Ex Vivo Study

Purpose Knee osteoarthritis (OA) is a musculoskeletal disorder characterised by abnormal joint motion, joint space narrowing, and cartilage degeneration. Early diagnosis is important to slow disease progression. Dynamic CT imaging adds three-dimensional functional information to an otherwise static diagnosis. This study investigates the diagnostic potential of inter-articular contact area during knee motion across three stages of cartilage degeneration. Methods Cartilage was progressively removed from the patellofemoral joint of a cadaveric knee to simulate stages of cartilage degeneration: first laterally, then at the crista, and finally medially. After each intervention, dynamic CT was performed during induced cyclic flexion-extension motion of the cadaveric knee. We quantified contact area dynamically by measuring distances between intact cartilage layers of the patella and femur. Contact areas across stages (baseline, lateral, crista, medial) were compared using the Wilcoxon Signed Rank test at six knee flexion angles (0°, 5°, 10°, 15°, 20°, 25°). Reproducibility was assessed by repeating the dynamic CT acquisition post-cartilage removal three times. Results Contact area increased significantly at each stage of cartilage degeneration compared to the previous stage (p < 0.05), progressing from 0 mm² to 84.2 mm², 176.0 mm², and 308.7 mm². For reproducibility, the standard error of the mean across three repetitions showed an average deviation of 6%. Differences varied across knee angles, with the least distinction observed in full extension. Spatially, the contact areas corresponded anatomically to the regions of cartilage removal. Conclusion Progressive cartilage removal in a cadaveric knee results in a significant increase in contact area.