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 moderate to good (kappa 0.50 and 0.62), worst in the patellofemoral joint and particularly at grade 3. On the common claim that MRI under-grades, 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.