Table 1.

Cartilage injure classification: Recht grade by MRI and Outerbridge classification through intraoperative assessment

Grade	Recht grade	Outerbridge classification
0	Normal	Normal
1	Focal low signal in cartilage with smooth cartilage surface	Cartilage softening and edema or blisters on the surface
2	Defect < 50% cartilage thickness	Superficial ulcers and fibrosis < 1 cm
3	Defect ≥ 50% cartilage thickness but not down to subchondral bone	Deep ulcers ≥ 1 cm with crab-like changes
4	Full-thickness cartilage defect with exposure of subchondral bone	Full-thickness cartilage tear, exposed subchondral bone