Example of non-sensitivity of radiography. (a) Baseline sagittal intermediate-weighted fat-suppressed image shows normal articular cartilage coverage in the medial femur and tibia. (b) At 24-month follow-up, there is circumscribed thinning of cartilage in the posterior medial femur (arrows). (c) Baseline radiograph does not show any abnormalities in regard to joint space width or any definite osteophytes at the medial tibia (no arrow). (d) At 24-month follow-up, no change is observed in comparison with the baseline image.