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