Table 1.

Modified Mankin grading system.

Category	Subcategory	Score
Surface integrity	Normal	0
	Slight surface irregularities	1
	Moderate surface irregularities	2
	Severe surface irregularities	3
	Clefts to transitional zone	4
	Clefts to radial zone	5
	Clefts to calcified zone	6
	Fibrillation and/or loss to transitional zone	7
	Fibrillation and/or loss to radial zone	8
	Fibrillation and/or loss to calcified zone	9
	Fibrillation and/or loss to subchondral bone	10
Cellularity	Normal	0
	Increase or slight decrease	1
	Moderate decrease	2
	Severe decrease	3
	No cells	4
Cell cloning	Normal	0
	Several doublets	1
	Many doublets	2
	Doublets and triplets	3
	Multiple cell nests	4
Safranin-O staining	Normal	0
	Slight reduction	1
	Reduction in radial layer	2
	Reduction in interterritorial layer	3
	Only present in pericellular matrix	4
	No staining	5
Total		0–23