Chondropathy and the modified Outerbridge system. Sample arthroscopic images demonstrating different grades of the modified Outerbridge scoring system. (a) Grade 0: smooth, firm articular cartilage. (b) Grade 1: articular cartilage is surface-intact, but softened. (c) Grade 2: articular cartilage with a damaged surface <50% of tissue depth. (d) Grade 3: articular cartilage with a damaged surface >50% of tissue depth. (e) Grade 4: articular cartilage with full-thickness tissue disruption extending to the subchondral bone.
Chu et al. Arthritis Research & Therapy 2012 14:212 doi:10.1186/ar3845