Table 1.

The Osteoarthritis Research Society International (OARSI) semi-quantitative scoring system for osteoarthritic change.

Score	Key feature
0	Normal
0.5	Loss of Safranin O staining without structural changes
1	Small fibrils without loss of cartilage
2	Vertical clefts down to the layer immediately below the superficial layer and some loss of surface lamina
3	Vertical clefts/erosions in the calcified cartilage involving <25% of the articular surface
4	Vertical clefts/erosion in the calcified cartilage involving 25–50% of the articular surface
5	Vertical clefts/erosion to the calcified cartilage involving 50–75% of the articular surface
6	Vertical clefts/erosion to the calcified cartilage involving >75% of the articular surface