Fig. 1

Representative data derived from the measurement of medial meniscal extrusion (MME) and medial tibial osteophyte distance by radiography, proton density-weighted magnetic resonance imaging (MRI), and T2 mapping MRI in the early-stage knee osteoarthritis joint. a Coronal fast spin echo proton density-weighted MRI with fat suppression. MME distance was measured as the distance from the outermost edge of the medial meniscus to a line connecting the femoral and tibial cortices. b Osteophyte distance measurement using radiography. c Osteophyte distance measurement using proton density-weighted MRI with fat suppression. d Definition of a boundary between the tibial cortex and osteophyte (high signal zone) using proton density-weighted imaging without fat suppression. e Osteophyte distance measurement using T2 mapping MRI. Dashed lines indicate cartilage and bone parts of the osteophyte. The line between bone part of osteophyte and tibial cortex was drawn by tracing the image obtained by proton density-weighted MRI without fat suppression. Bp Bone part of osteophyte, Cp Cartilage part of osteophyte, M Meniscus