Table 2.

The modified O'Driscoll histologic score.

Characteristic		Score
% hyaline cartilage	80–100	8
	60–80	6
	40-60	4
	20-40	2
	0-20	0
Structural characteristics
Surface irregularity	Smooth and intact	2
	Fissures	1
	Severe disruption, fibrillation	0
Structural integrity	Normal	2
	Slight disruption, including cysts	1
	Severe lack of integration	0
Thickness	100% of normal adjacent cartilage	2
	50% to 100% or thicker than normal	1
	0–50%	0
Bonding to adjacent cartilage	Bonded at both ends of graft	2
	Bonded at one end/partially both ends	1
	Not bonded	0
Freedom from cellular changes of degeneration	Normal cellularity, no clusters	2
	Slight hypocellularity, <25% chondrocyte clusters	1
	Moderate hypocellularity, >25% clusters	0
Freedom from degenerate changes in adjacent cartilage	Normal cellularity, no clusters, normal staining	3
	Normal cellularity, mild clusters, moderate staining	2
	Mild or moderate hypocellularity, slight staining	1
	Severe hypocellularity, slight staining	0
Reconstitution of subchondral bone	Complete reconstitution	2
	Greater than 50% reconstruction	1
	50% or less reconstruction	0
Bonding of repair cartilage to de novo subchondral bone	Complete and uninterrupted	2
	<100% but >50% reconstruction	1
	<50% complete	0
Safranin O staining	>80% homogeneous positive stain	2
	40%–80% homogeneous positive stain	1
	<40% homogeneous positive stain	0
	Total score	Max 27