Table I.
Cartilage histopathology grade methodology guide modified from Pritzker et al25
| Grade* (key features) | Associated criteria (tissue reaction) | |
|---|---|---|
| Grade 0: surface intact, cartilage morphology intact | ||
| Matrix: normal structure | ||
| Cells: intact, appropriate orientation, tide mark can be seen | ||
| Grade 1: surface intact | ||
| Matrix: superficial zone intact, oedema and/or superficial fibrillation (abrasion), focal superficial matrix condensation | ||
| Cells: death, hypertrophy, superficial zone reaction has higher level of superficial fibrillation | ||
| Grade 2: surface discontinuity | ||
| As above | ||
| Matrix discontinuity at superficial zone (deep fibrillation) | ||
| 1/3 of upper cartilage staining loss (Safranin-O or Toluidine blue) | ||
| Increased perichondral (mid-zone) staining | ||
| Cells: death, hypertrophy | ||
| Grade 3: vertical fissures | ||
| As above | ||
| Matrix fissures into mid zone, branched fissures | ||
| 2/3 of cartilage staining loss (into deep zone) | ||
| New collagen formation (polarised light microscopy | ||
| Cells: death, regeneration (clusters), hypertrophy, cartilage domains adjacent to fissures | ||
| Grade 4: erosion | ||
| Cartilage matrix loss: delamination of superficial layer | ||
| Mid-layer cyst formation | ||
| Matrix loss in superficial layer and mid-zone regions | ||
| Grade 5: denudation | ||
| Sclerotic bone or reparative tissue found within denuded surface | ||
| Microfracture with repair at bone surface only | ||
| Grade 6: deformation | ||
| Bone remodeling with osteophyte formation | ||
| Microfracture with extensive cartilaginous and osseous repair |