Published Date: 31st October 2025
Publication Authors: Iyengar. KP
Background: Dual-energy X-ray absorptiometry (DEXA) remains the gold standard test for the assessment of bone density. In a previous Magnetic Resonance Imaging (MRI) study of the lumbar spine it has been noted that when the T1 vertebral body/CSF (cerebrospinal fluid) ratio is high it is suggestive of osteoporosis.
Purpose: The aim of this study is to investigate whether the relative signal intensity of the imaged bone marrow in the knee compared to the other structures can also be used to detect osteoporosis.
Patients and methods: A total of 103 patients who had undergone both a knee MRI and a DEXA scan within the same 12-month period were identified. The T1/PD (Proton Density) and FS (Fat Suppression) signal intensity of marrow (of the femur, tibia and patella), vastus medialis muscle, joint fluid and subcutaneous fat were measured within a region of interest, and the signal intensity ratios were calculated. The ratios were stratified as normal, osteopenic, or osteoporotic based on DEXA T-scores. The correlation between the signal intensity ratios and the DEXA T-score was evaluated using Pearson's linear coefficient and ROC analysis. Intraclass correlation coefficients (ICC) were also calculated.
Results: The bone marrow (FS)/joint fluid (FS) ratio was significantly higher in the osteoporotic group than in the normal and osteopenic groups (femoral p = 0.0018, patellar bone marrow (tibia) p = 0.0003 and pooled p = 0.0022). The intraobserver (ICC = 0.923-0.974) and interobserver reliability (ICC = 0.803-0.945) were excellent.
Conclusion: The bone marrow/joint fluid (FS) ratios of the knee MRI have some predictive value for the presence of osteoporosis.
Petrou, E.; Iyengar, K.P. et al. (2025). Predictive Value of Magnetic Resonance Imaging of the Knee in the Evaluation/Quantification of Osteoporosis: A Comparative Analysis With Dual-Energy X-Ray Absorptiometry. Journal of medical imaging and radiation oncology. Oct 31(E-pub ahead of print) [Online]. Available at: https://doi.org/10.1111/1754-9485.70038 [Accessed 5 November 2025].
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