Table 2 The modified O’Driscoll histologic score

I. % Hyaline cartilage

80–100

Score

60–80

8

40–60

6

20–40

4

0–20

2

II. Structural characteristics

0

A. Surface irregularity

Smooth and intact

Fissures

2

Severe disruption, fibrillation

1

B. Structural integrity

Normal

0

Slight disruption, including cysts

2

Severe lack of integration

1

C. Thickness

100% of normal adjacent cartilage

0

50% to 100% or thicker than normal

2

0–50%

1

D. Bonding to adjacent cartilage

Bonded at both ends of graft

0

Bonded at one end/partially both ends

2

Not bonded

1

III. Freedom from cellular changes of degeneration

Normal cellularity, no clusters

0

Slight hypocellularity, <25% chondrocyte clusters

2

Moderate hypocellularity, >25% clusters

1

IV. Freedom from degenerate changes in adjacent cartilage

Normal cellularity, no clusters, normal staining

0

Normal cellularity, mild clusters, moderate staining

3

Mild or mod hypocellularity, slight staining

2

Severe hypocellularity, slight staining

1

V. Reconstitution of subchondral bone

Complete reconstitution

0

Greater than 50% recon

2

50% or less recon

1

VI. Bonding of repair cartilage to de novo subchondral bone

Complete and uninterrupted

0

<100% but >50% recon

2

<50% complete

1

VII. Safrinin O staining

>80% homogeneous positive stain

0

40%–80% homogeneous positive stain

2

<40% homogeneous positive stain

1

Total score

0

Max27