Table 1.
Histological Inverse Grading System for the Evaluation of the Articular Cartilage Repair Tissues According to Sellers et al.10
| Filling of the defect relative to surface of normal adjacent cartilage | |
| 111%–125% | 1 |
| 91%–110% | 0 |
| 76%–90% | 1 |
| 51%–75% | 2 |
| 26%–50% | 3 |
| <25% | 4 |
| Integration of repair tissue with surrounding articular cartilage | |
| Normal continuity and integration | 0 |
| Decreased cellularity | 1 |
| Gap or lack of continuity on one side | 2 |
| Gap or lack of continuity on two sides | 3 |
| Matrix staining with Safranin O-fast green | |
| Normal | 0 |
| Slightly reduced | 1 |
| Moderately reduced | 2 |
| Substantially reduced | 3 |
| None | 4 |
| Cellular morphology (chose first between a-b-c-d) | |
| (a) Normal | 0 |
| (b) Mostly round cells with the morphology of chondrocytes | |
| >75% of tissue with columns in radial zone | 0 |
| 25%–75% of tissue with columns in radial zone | 1 |
| <25% of tissue with columns in radial zone (disorganized) | 2 |
| (c) 50% round cells with the morphology of chondrocytes | |
| >75% of tissue with columns in radial zone | 2 |
| 25%–75% of tissue with columns in radial zone | 3 |
| <25% of tissue with columns in radial zone (disorganized) | 4 |
| (d) Mostly spindle-shaped (fibroblast-like) cells | 5 |
| Architecture within entire defect (not including margins) | |
| Normal | 0 |
| 1–3 small voids | 1 |
| 1–3 large voids | 2 |
| >3 large voids | 3 |
| Clefts or fibrillations | 4 |
| Architecture of surface | |
| Normal | 0 |
| Slight fibrillation or irregularity | 1 |
| Moderate fibrillation or irregularity | 2 |
| Severe fibrillation or disruption | 3 |
| Percentage of new subchondral bone | |
| 90%–100% | 0 |
| 75%–89% | 1 |
| 50%–74% | 2 |
| 25%–49% | 3 |
| <25% | 4 |
| Formation of tidemark | |
| Complete | 0 |
| 75%–99% | 1 |
| 50%–74% | 2 |
| 25%–49% | 3 |
| <25% | 4 |
| Total score | 0–31 |