Table 3 Modified O’Driscoll Histology Score[13]

I

% Hyaline Cartilage:

80-100

8

60-80

6

40-60

4

20-40

2

0-20

0

II

Structural

A. Surface irregularity:

Smooth and intact

2

Characteristics:

Fissures

1

Severe disruption, fibrillation

0

B. Structural integrity:

Normal

2

Slight disruption, including cysts

1

Severe lack of integration

0

C. Thickness:

100% of normal adjacent cartilage

2

50-100% or thicker than normal

1

0-50%

0

D. Bonding to adjacent cartilage:

Bonded at both ends of graft

2

Bonded at one end/partially both ends

1

Not bonded

0

III

Freedom from cellular changes of degeneration:

Normal cellularity, no clusters

2

Slight hypocellularity, <25% chondrocyte clusters

1

Moderate hypocellularity, >25% clusters

0

IV

Freedom from degenerate changes in adjacent cartilage:

Normal cellularity, no clusters, normal staining

3

Normal cellularity, mild clusters, moderate staining

2

Mild or mod hypocellularity, slight staining

1

Severe hypocellularity, slight staining

0

V

Reconstitution of subchondral bone:

complete reconstitution

2

greater than 50% reconstitution

1

50% or less reconstitution

0

VI

Bonding of repair cartilage to denovo subchondral bone:

complete and uninterrupted

2

<100% but >50% recon

1

<50% complete

0

VII

Safranin O staining:

> 80% homogenous positive stain

2

40-80% homogenous positive stain

1

<40% homogenous positive stain

0

TOTAL SCORE

Max 27