Table 2 Mankin's histological histochemical grading
| Category | Grade |
|---|---|
| I. Structure | |
| Normal | 0 |
| Surface irregularities | 1 |
| Pannus and surface irregularities | 2 |
| Clefts to transitional zone | 3 |
| Clefts to radial zone | 4 |
| Clefts to calcified zone | 5 |
| Complete disorganization | 6 |
| II. Cells | |
| Normal | 0 |
| Diffuse hypercellularity | 1 |
| Cloning | 2 |
| Hypocellularity | 3 |
| III. Safranin-O staining | |
| Normal | 0 |
| Slightly reduced | 1 |
| Moderate reduced | 2 |
| Severe reduced | 3 |
| No dye noted | 4 |
| IV. Tidemark integrity | |
| Intact | 0 |
| Crossed by blood vessels | 1 |