Table 2.

Modified Mankin score (criteria for histological evaluation).

Safranin O-fast green staining  0 = uniform staining throughout articular cartilage  1 = loss of staining in the superficial zone for less than one-half of the length of the plateau  2 = loss of staining in the superficial zone for one-half or more of the length of the plateau  3 = loss of staining in the superficial and middle zones for less than one-half of the length of the plateau  4 = loss of staining in the superficial and middle zones for one-half or more of the length of the plateau  5 = loss of staining in all 3 zones for less than one-half of the length of the plateau  6 = loss of staining in all 3 zones for one-half or more of the length of the plateau

Chondrocyte loss  0 = no decrease in cells  1 = minimal decrease in cells  2 = moderate decrease in cells  3 = marked decrease in cells  4 = very extensive decrease in cells

Structure  0 = normal  1 = surface irregularities  2 = 1-3 superficial clefts  3 = >3 superficial clefts  4 = 1-3 clefts extending into the middle zone  5 = >3 clefts extending into the middle zone  6 = 1-3clefts extending into the deep zone  7 = >3 clefts extending into the deep zone  8 = clefts extending to calcified cartilage