The prevalence of knee osteoarthritis is traditionally based on radiographic findings, but magnetic resonance imaging is now being used to provide better visualization of bone, cartilage, and soft tissues as well as the patellar compartment. The goal of this study was to estimate the prevalences of knee features defined on magnetic resonance imaging in a population and to relate these abnormalities to knee osteoarthritis severity scores based on radiographic findings, physical functioning, and reported knee pain in middle-aged women.
Magnetic resonance images of the knee were evaluated for the location and severity of cartilage defects, bone marrow lesions, osteophytes, subchondral cysts, meniscal and/or ligamentous tears, effusion, and synovitis among 363 middle-aged women (724 knees) from the Michigan Study of Women's Health Across the Nation. These findings were related to Kellgren-Lawrence osteoarthritis severity scores from radiographs, self-reported knee pain, self-reported knee injury, perception of physical functioning, and physical performance measures to assess mobility. Radiographs, physical performance assessment, and interviews were undertaken at the 1996 study baseline and again (with the addition of magnetic resonance imaging assessment) at the follow-up visit during 2007 to 2008.
The prevalence of moderate-to-severe knee osteoarthritis changed from 3.7% at the baseline assessment to 26.7% at the follow-up visit eleven years later. Full-thickness cartilage defects of the medial, lateral, and patellofemoral compartments were present in 14.5% (105 knees), 4.6% (thirty-three knees), and 26.2% (190 knees), respectively. Synovitis was identified in 24.7% (179) of the knees, and joint effusions were observed in 70% (507 knees); 21.7% (157) of the knees had complex or macerated meniscal tears. Large osteophytes, marked synovitis, macerated meniscal tears, and full-thickness tibial cartilage defects were associated with increased odds of knee pain and with 30% to 40% slower walking and stair-climbing times.
Middle-aged women have a high prevalence of moderate-to-severe knee osteoarthritis corroborated by strong associations with cartilage defects, complex and macerated meniscal tears, osteophytes and synovitis, knee pain, and lower mobility levels.