Medial meniscus extrusion is invariably observed and consistent with tibial osteophyte width in elderly populations: The Bunkyo Health Study

We reported that full-length width of medial tibial osteophyte composed of cartilage and bone parts is directly correlated with medial meniscus extrusion (MME) in early-stage knee osteoarthritis (OA). However, no data are available for MME prevalence and its relationship to osteophyte in elderlies. 1,191 elderlies (females 57%; 72.9 years old on average) in the Bunkyo Health Study underwent standing plain radiograph and proton density-weighted MRI on knee joints. MRI-detected OA changes were evaluated according to the Whole Organ Magnetic Resonance Imaging Score. A new method to assess cartilage and bone parts of osteophyte was developed by pseudo-coloring images of proton density-weighted fat-suppressed MRI. Most of the subjects showed the Kellgren-Lawrence grade 1 or 2 of radiographic medial knee OA (88.1%), MME (98.7%, 3.90 ± 2.01 mm) and medial tibial osteophyte (99.3%, 3.27 ± 1.50 mm). Among the OA changes, MME was most closely associated with full-length width of medial tibial osteophyte (β = 1.114; 95%CI, 1.069–1.159; p