KEY diagnostic marker for axial spondyloarthritis (axSpA), sacroiliac bone marrow oedema (BMO), may be far more common in the general population than previously recognised. Findings from a large population-based German cohort study raised concerns about the diagnostic criteria for axSpA.
Large MRI Analysis Finds Sacroiliac BMO in Nearly One-Third of Adults
Researchers analysed more than 11,000 MRI scans from adults ages 20-69 to determine how frequently BMO occurs outside inflammatory disease settings. Using expert radiology review and an AI deep-learning algorithm, approximately 30% of the participants were found to have BMO. This is around 50 times higher than the reported prevalence of axSpA in the population.
Women demonstrated higher rates of BMO than men, while elevated BMI, physically demanding occupations, and intensive recreational physical activity were also associated with increased prevalence. Overweight participants had some of the strongest associations with BMO, with ≥25 linked to a significantly increased likelihood of oedema.
MRI Abnormalities May Reflect Mechanical Stress Rather Than Inflammatory Disease
The authors highlighted that previous smaller studies had identified similar MRI changes in athletes and postpartum women, but this was the first large-scale population-based study to establish reference prevalence data in the general adult population.
It was noted that MRI-detected BMO is currently considered a key imaging marker for diagnosing axSpA and can influence decisions regarding biologic anti-inflammatory treatment. However, these findings suggest many MRI abnormalities may reflect mechanical stress or physiological changes rather than inflammatory disease.
Findings Could Help Reduce Misdiagnosis and Unnecessary Treatment
Researchers concluded that isolated MRI findings of sacroiliac bone marrow oedema should be interpreted alongside clinical history, demographic factors, and symptoms rather than used in isolation to diagnose inflammatory disease.
The authors suggested the findings could support the development of more specific MRI thresholds and diagnostic algorithms to improve accuracy and reduce inappropriate initiation of biologic therapies.
They added that the data provide important population-level reference information for clinicians interpreting MRI scans in suspected axial spondyloarthritis cases.
Reference
Bressem K et al. Prevalence and determinants of sacroiliac joint bone marrow oedema in the general population in Germany: a population-based cross-sectional study. Lancet Rheumatol. 2026;DOI:10.1016/S2665-9913(26)00071-8.
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