Table 1 Histological score criteria

Inflammation

0

Normal

1

Minor infiltration of inflammatory cells at periphery of the joint

2

Moderate infiltration – inflammatory pannus < 50 % joint area

3

Marked infiltration – inflammatory pannus > 50 % joint area

Intervertebral disc destruction

0

Normal

1

Less than 50 % disc destruction

2

More than 50 % disc destruction

3

Total disc destruction/only necrotic disc left

Cartilage damage

0

Normal

1

Some loss of articular cartilage or growth plate cartilage or both

2

Severe loss of articular cartilage and some growth plate cartilage damage

3

Severe loss of articular cartilage and severe growth plate cartilage damage

Bone erosion

0

Normal

1

One or a few small areas of resorption in original vertebral bone.

2

Numerous areas of obvious focal resorption in original vertebral bone or several areas of severe destruction.

Excess tissue formation (excluding inflammatory infiltrate)

0

Normal

1

Mesenchymal cell invasion or expansion or both

2

Moderate fibrocartilage formation (<50 % of the original disc area)

3

Extensive fibrocartilage formation (>50 % of the original disc area)

Ectopic chondrocytes/chondrophyte

0

Normal

1

Single small area

2

Single large area

3

Multiple areas