Table 1.

An overview of the MRI-based modified Outerbridge grade [3] and the intraoperative Beck’s grade [5]

Modified Outerbridge grade	Beck’s grade
0 = Normal cartilage	1 = Normal
1 = Signal changes and/or minor surface irregularities	2 = Malacia (roughening of surface, fibrillation)
2 = Cartilage thickness loss ≤ 50%	3 = Debonding (loss of fixation to the subchondral bone; carpet phenomenon)
3 = Cartilage thickness loss > 50%	4 = Cleavage (loss of fixation to the subchondral bone; frayed edges, thinning of the cartilage flap)
4 = Total cartilage loss	5 = Full-thickness defect, complete loss of cartilage