Example of non-specificity of radiography. (a) Baseline sagittal intermediate-weighted fat-suppressed image shows discrete superficial cartilage loss at the central part of the medial femur (arrows). (b) No progression is seen at 24-month follow-up (arrowheads). (c) Radiographic joint space narrowing is depicted at baseline (arrowheads). (d) Further decrease in joint space width is shown at 24-month follow-up (arrows) and was due to meniscal extrusion (not shown).