Background Knee MRI is increasingly used to inform clinical management. Features associated with osteoarthritis are often present in asymptomatic uninjured knees; however, the estimated prevalence varies substantially between studies. We performed a systematic review with meta-analysis to provide summary estimates of the prevalence of MRI features of osteoarthritis in asymptomatic uninjured knees.
Methods We searched six electronic databases for studies reporting MRI osteoarthritis feature prevalence (ie, cartilage defects, meniscal tears, bone marrow lesions and osteophytes) in asymptomatic uninjured knees. Summary estimates were calculated using random-effects meta-analysis (and stratified by mean age: <40 vs ≥40 years). Meta-regression explored heterogeneity.
Results We included 63 studies (5397 knees of 4751 adults). The overall pooled prevalence of cartilage defects was 24% (95% CI 15% to 34%) and meniscal tears was 10% (7% to 13%), with significantly higher prevalence with age: cartilage defect <40 years 11% (6%to 17%) and ≥40 years 43% (29% to 57%); meniscal tear <40 years 4% (2% to 7%) and ≥40 years 19% (13% to 26%). The overall pooled estimate of bone marrow lesions and osteophytes was 18% (12% to 24%) and 25% (14% to 38%), respectively, with prevalence of osteophytes (but not bone marrow lesions) increasing with age. Significant associations were found between prevalence estimates and MRI sequences used, physical activity, radiographic osteoarthritis and risk of bias.
Conclusions Summary estimates of MRI osteoarthritis feature prevalence among asymptomatic uninjured knees were 4%–14% in adults aged <40 years to 19%–43% in adults ≥40 years. These imaging findings should be interpreted in the context of clinical presentations and considered in clinical decision-making.
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Contributors AGC, BEØ and KMC: designed the study and planned the analyses. AGC and HFH: completed all searches and study selection (including inclusion and exclusion of abstracts). AGC and JJS: completed all data extraction. AGC and BEØ: completed all risk of bias assessment. AG: completed all critical appraisals of magnetic resonance imaging sequences. AGC: did the meta-analyses and meta-regressions, wrote the initial draft. All authors interpreted the data, critically revised the manuscript for important intellectual content and approved the final version of the manuscript.
Funding AGC was supported by postdoctoral funding from a European Union Seventh Framework Programme (FP7-PEOPLE-2013-ITN; 607510), and is a recipient of a National Health and Medical Research Council (NHMRC) of Australia Early Career Fellowship (Neil Hamilton Fairley Clinical Fellowship, APP1121173). HFH is supported by a NHMRC Project Grant (GNT1106852). JJS is supported by an Institutional DevelopmentAward (IDeA) from the National Institute of General Medical Sciences of theNational Institutes of Health (U54-GM104941). The funders had no role in any part of the study or in any decision about publication.
Disclaimer These sources had no involvement in study design, interpretation of data, writing of the manuscript or the decision to submit the manuscript for publication. All other authors declare no competing interests.
Competing interests AG is president of Boston Imaging Core Lab, LLC, and a consultant to Merck Serono, Genzyme, OrthoTrophix and TissueGene.
Provenance and peer review Not commissioned; externally peer reviewed.
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