Background Although magnetic resonance imaging (MRI) has been proved to be far more sensitive than conventional radiographs to detect OP, the natural history of MRI-detected OP in older adults has not yet been described, and it is unclear whether knee structural abnormalities, including cartilage defects, cartilage volume, bone marrow lesions (BMLs), meniscal extrusion, infrapatellar fat pad (IPFP), and effusion-synovitis, can predict osteophyte change.
Objectives To describe the natural history of knee MRI-detected OP, and to determine if knee structural risk factors are associated with change of MRI-detected OP in a longitudinal study of older adults.
Methods 413 randomly selected older adults (mean age 63 years) had magnetic resonance imaging at baseline and approximately 2.6 years later to measure knee OP, cartilage defect, cartilage volume, BMLs, meniscal extrusion, IPFP quality score/maximum area and effusion-synovitis. Weight, height, body mass index (BMI) and leg muscle strength were measured by standard protocols.
Results 85% participants had MRI-detected OP at baseline. Over 2.6 years, the average OP score increased significantly in all compartments. The OP score remained stable in 53% participants and worsened in 46% (≥1-point increase) OP, with 1% decreasing. Baseline factors associated with an increase in MRI-detected OPs over 2.6 years included BMI, cartilage defects, BMLs, meniscal extrusion, IPFP quality score and Effusion. In multivariable analyses, baseline cartilage defects, BMLs and meniscal extrusions and IPFP quality score were site-specifically and significantly associated with increased OP at medial tibiofemoral, lateral tibiofemoral and total compartments (p all <0.05). In contrast, total and suprapatellar pouch effusion-synovitis were significantly associated with increased OP at total and lateral compartments (p all <0.01). The significant associations between baseline cartilage volume and increased OPs at medial and total compartments became non-significant after further adjustment for other knee structural abnormalities. Age sex and smoking status were not associated with increased OPs over time.
Conclusions Knee MRI-detected OP in older adults is common and, in contrast to radiographs, is likely to progress over a relatively short period. Progression can be predicted by structural risk factors suggesting they are a consequence of these abnormalities.
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Acknowledgements The authors thank the participants who made this study possible, and acknowledge the role of the staff and volunteers in collecting the data, particularly research nurses Boon C and Boon P. Warren R assessed MRIs and Dr Srikanth V and Dr Cooley H assessed radiographs.
Disclosure of Interest None declared