Differences in tibial subchondral bone structure evaluated using plain radiographs between knees with and without cartilage damage or bone marrow lesions - the Oulu Knee Osteoarthritis study

OBJECTIVES: To investigate whether subchondral bone structure from plain radiographs is different between subjects with and without articular cartilage damage or bone marrow lesions (BMLs). METHODS: Radiography-based bone structure was assessed from 80 subjects with different stages of knee osteoarthritis using entropy of Laplacian-based image (E(Lap)) and local binary patterns (E(LBP)), homogeneity index of local angles (HI(Angles,mean)), and horizontal (FD(Hor)) and vertical fractal dimensions (FD(Ver)). Medial tibial articular cartilage damage and BMLs were scored using the magnetic resonance imaging osteoarthritis knee score. Level of statistical significance was set to p < 0.05. RESULTS: Subjects with medial tibial cartilage damage had significantly higher FD(Ver) and E(LBP) as well as lower E(Lap) and HI(Angles,mean) in the medial tibial subchondral bone region than subjects without damage. FD(Hor), FD(Ver), and E(LBP) were significantly higher, whereas E(Lap) and HI(Angles,mean) were lower in the medial trabecular bone region. Subjects with medial tibial BMLs had significantly higher FD(Ver) and E(LBP) as well as lower E(Lap) and HI(Angles,mean) in medial tibial subchondral bone. FD(Hor), FD(Ver), and E(LBP) were higher, whereas E(Lap) and HI(Angles,mean) were lower in medial trabecular bone. CONCLUSIONS: Our results support the use of bone structural analysis from radiographs when examining subjects with osteoarthritis or at risk of having it. KEY POINTS: • Knee osteoarthritis causes changes in articular cartilage and subchondral bone • Magnetic resonance imaging is a comprehensive imaging modality for knee osteoarthritis • Radiography-based bone structure analysis can provide additional information of osteoarthritic subjects