Objective: (1) To describe the natural history of subchondral bone marrow lesions (BMLs) in a sample of subjects with knee osteoarthritis (OA) or at risk of developing it. (2) To examine the association of change in BMLs from baseline (BL) to 30-month follow-up (FU) with the risk of cartilage loss in the same subregion at FU.
Methods: 1.0T MRI was performed using proton density-weighted fat-suppressed sequences. BML size and cartilage status were scored in the same subregions according to the WORMS system. Subregions were categorized based on comparison of BL and FU BML status. A logistic regression model was used to assess the association of change in BML status with cartilage loss over 30 months using stable BMLs as the reference group.
Results: 395 knees were included. 66% of prevalent BMLs changed in size; 50% showed either regression or resolution at FU. The adjusted odds ratios [95% confidence intervals] of cartilage loss in the same subregion at FU for the different groups were 1.2 [0.5,1.6] for regressing BMLs, 0.9 [0.5,1.6] for resolving BMLs, 2.8 [1.5,5.2] for progressing BMLs, 0.2 [0.1,0.3] for subregions with no BMLs at BL and FU, and 3.5 [2.1,5.9] for newly developing BMLs. BML size at baseline was associated with risk of subsequent cartilage loss.
Conclusions: The majority of pre-existing BMLs decreased in size at FU. Absence of BMLs was associated with a decreased risk of cartilage loss while progressing and new BMLs showed a high risk of cartilage loss in the same subregion.