Sensitivity and associations with pain and body weight of an MRI definition of knee osteoarthritis compared with radiographic Kellgren and Lawrence criteria: A population-based study in middle-aged females

Objectives: Is amagnetic resonance imaging (MRI) definition for tibiofemoral osteoarthritis [(TFOA_MRI) (definite osteophyte and full-thickness cartilage loss (or a combination of these factors with other MRI osteoarthritis (OA) features)] more sensitive to detect structural OA compared with the Kellgren & Lawrence (K&L) grading? And which definition shows the strongest association with (1) knee pain at baseline, (2) persistent knee pain during 2-year follow-up, (3) new onset of knee pain ±2 years later, and (4) body mass index (BMI). Design: Of 888 females of the open population Rotterdam Study, radiographs and MRI of both knees were assessed for knee OA defined by K&L≥2 and TFOA_MRI. Pain in or around the knee is measured at baseline and ±2 years later. GEE analyses are used for the associations. Results: Of 1766 knees, 77 knees (4%) were diagnosed with K&L≥2, whereas 160 knees (9%) met the TFOA_MRI criteria. Only 43 knees met both definitions (34 knees were graded with K&L≥2 and no TFOA_MRI and 117 knees met only the TFOA_MRI criteria). The association between the definitions and knee pain at baseline was higher when TFOA_MRI was included [TFOA_MRI alone: odds ratio (OR)=2.83 (95% confidence interval (CI): 1.84-4.36); TFOA_MRI & K&L≥2: OR=6.28 (95% CI: 2.99-13.19)] than for K&L≥2 alone (OR=1.83 (95% CI: 0.63-5.32)). This was similar for the association between the definitions and persistent knee pain, and between the definitions and BMI. Conclusions: TFOA_MRI detects more cases of knee OA than K&L≥2. Together with a better content validity and at least equal construct validity, we conclude that the TFOA_MRI definition for knee OA is more sensitive in detecting structural knee OA.