Do Existing MRI Definitions of Knee Osteoarthritis Identify Knees That Will Develop Clinically Significant Disease Over Up To 11 Years of Follow‐Up?

Objectives In individuals without radiographic knee osteoarthritis (KOA), we investigated whether MRI‐defined KOA at baseline was associated with incident radiographic and symptomatic disease during up to 11 years of follow‐up. Methods Osteoarthritis Initiative participants without tibiofemoral radiographic KOA at baseline were assessed for MRI‐based tibiofemoral cartilage damage, osteophyte presence, bone marrow lesions, and meniscal damage/extrusion. We defined MRI KOA using alternative, reported definitions (Def A and Def B). Kellgren‐Lawrence (KL) grade, joint space narrowing (JSN), and frequent knee symptoms (Sx) were assessed at baseline, 1‐, 2‐, 3‐, 4‐, 6‐, 8‐, and 10/11‐year follow‐up visits. Incident tibiofemoral radiographic KOA (outcome) was defined as (1) KL ≥ 2, (2) KL ≥ 2 and JSN, or (3) KL ≥ 2 and Sx. Adjusted Cox proportional hazards regression models examined associations of baseline MRI‐defined KOA (Def A and Def B) with incident outcomes during up to 11 years of follow‐up. Results Among 1621 participants [mean age=58.8 (SD=9.0) years, mean BMI=27.2 (4.5) kg/m 2 , 59.5% women], 17% had MRI‐defined KOA by Def A and 24% by Def B. Baseline MRI‐defined KOA was associated with incident KL ≥ 2 [odds ratio=2.94 (95% CI=2.34‐3.68) for Def A and 2.44 (95% CI=1.97‐3.03) for Def B]. However, a substantial proportion of individuals with baseline MRI‐defined KOA did not develop incident KL ≥ 2 during follow‐up (59% for Def A and 64% for Def B). Findings were similar for the other two outcomes. Conclusions Current MRI definitions of KOA do not adequately identify knees that will develop radiographic and symptomatic disease.