Sagittal PD-weighted TSE MRI of a 41-year-old male. A defect of more than 50% of the cartilage thickness at the medial femoral condyle is visible (white arrow). This finding is defined as grade 3 disease. A grade 2 disorder as a superficial fibrillation or erosion composing less than 50% of the cartilage was noticed at the tibial medial plateau (black arrow).