Arthroscopy vs. MRI for a detailed assessment of cartilage disease in osteoarthritis: diagnostic value of MRI in clinical practice

von Engelhardt LV, Lahner M, Klussmann A, Bouillon B, et al. · BMC Musculoskeletal Disorders

Agreement between MRI and arthroscopy was only moderate to good (kappa 0.50 and 0.62), worst in the patellofemoral joint and particularly at grade 3. Directly against a common claim: the authors looked for a tendency for MRI to under-grade and report that one 'was not noticed'. MRI grading is imprecise rather than reliably biased low.

Population

36 patients with clinically relevant knee osteoarthritis

Intervention

Standardized 1.5-T MRI graded by two blinded readers

Comparator

Arthroscopic grading of the same knees within three months

Limitations

Small (n=36), single-center, 1.5 T, and up to three months between scan and scope — long enough for real change in some knees.