Observations of early structural changes over 6 years on magnetic resonance imaging in knees without radiographic...

To describe longitudinal changes of Magnetic Resonance Imaging (MRI) features in the medial vs lateral tibiofemoral (TF) and patellofemoral (PF) compartments, in knees with no radiographic osteoarthritis (OA) at baseline.

In 340 individuals from the Osteoarthritis Initiative aged 45-55 years (51% women) with 430 knees at risk for OA and 250 not at risk, we assessed MRI scans of both knees using the MRI OA Knee Score system. A change in a feature from baseline to 6 years was defined as ≥1 grade increase in ≥1 subregion. We compared risk for structural changes across knee compartments and by risk status using mixed effects Poisson regression.

MRI changes over 6 years were common, with 89% of persons (76% of knees) showing increased cartilage damage, 50% (37%) in osteophytes, 75% (57%) in Bone Marrow Lesions (BMLs), and 28% (18%) with meniscal damage. Changes were most common in the PF joint, with risk ratios (RR) vs lateral TF joint of 2.4 (95% CI 1.9-3.0) for cartilage damage, 1.3 (1.2-1.5) for osteophytes and 2.8 (2.3-3.4) for BMLs. The risk of meniscal damage in the medial TF was higher compared to the lateral TF (RR 2.8 [1.9-4.1]). At-risk knee status was associated with an increased risk of meniscal damage (RR 1.8 [1.2-2.7]) but weakly with changes in cartilage damage, osteophytes, or BMLs.

Increase in structural damage occurs in majority of knees with Kellgren-Lawrence 0 at baseline, irrespectively of presence of OA risk factors. Most early changes occurred in the PF joint.