Prevalence of abnormalities in knees detected by MRI in adults without knee osteoarthritis: population based observational study (Framingham Osteoarthritis Study)

Abstract

Objective: To examine use of magnetic resonance imaging (MRI) of knees with no radiographic evidence of osteoarthritis to determine the prevalence of structural lesions associated with osteoarthritis and their relation to age, sex, and obesity.

Design: Population based observational study.

Setting: Community cohort in Framingham, MA, United States (Framingham osteoarthritis study).

Participants: 710 people aged >50 who had no radiographic evidence of knee osteoarthritis (Kellgren-Lawrence grade 0) and who underwent MRI of the knee.

Main outcome measures: Prevalence of MRI findings that are suggestive of knee osteoarthritis (osteophytes, cartilage damage, bone marrow lesions, subchondral cysts, meniscal lesions, synovitis, attrition, and ligamentous lesions) in all participants and after stratification by age, sex, body mass index (BMI), and the presence or absence of knee pain. Pain was assessed by three different questions and also by WOMAC questionnaire.

Results: Of the 710 participants, 393 (55%) were women, 660 (93%) were white, and 206 (29%) had knee pain in the past month. The mean age was 62.3 years and mean BMI was 27.9. Prevalence of "any abnormality" was 89% (631/710) overall. Osteophytes were the most common abnormality among all participants (74%, 524/710), followed by cartilage damage (69%, 492/710) and bone marrow lesions (52%, 371/710). The higher the age, the higher the prevalence of all types of abnormalities detectable by MRI. There were no significant differences in the prevalence of any of the features between BMI groups. The prevalence of at least one type of pathology ("any abnormality") was high in both painful (90-97%, depending on pain definition) and painless (86-88%) knees.

Conclusions: MRI shows lesions in the tibiofemoral joint in most middle aged and elderly people in whom knee radiographs do not show any features of osteoarthritis, regardless of pain.

Fig 1 Selection process of knees included in present study

Fig 2 Knee with multiple abnormalities on MRI indicating early stage osteoarthritis despite lack of radiographic osteoarthritis. A: coronal fat suppressed proton density weighted image shows several features of early OA detectable only by MRI. White arrowhead shows focal full thickness cartilage defect at central weight bearing part of medial femur. In addition there is adjacent subchondral bone marrow lesion presenting as area of ill defined hyperintensity (arrows). Black arrowheads show meniscal extrusion at medial joint line causing bulging of neighbouring medial collateral ligament (no arrow). B: sagittal proton density weighted image shows isolated degenerative horizontal oblique tear of posterior horn of medial meniscus extending to undersurface of meniscus adjacent to posterior tibial surface (arrows). No associated cartilage damage or subchondral bony alterations are seen

Fig 3 Prevalence of osteoarthritis features on MRI in knees without radiographic osteoarthritis stratified by age group with standard and more stringent definitions of MRI abnormalities