Grading system of articular cartilage degeneration in osteoarthritis of the knee.

Degenerative findings observed in the articular cartilage of the knee during high tibial osteotomy with arthrotomy, unicompartmental arthroplasty, or total replacement were classified into 9 grades: Grade 0--normal, Grade I--yellow discoloration, Grade II--softening and unevenness, Grade III--fasciculation and attrition, Grade IV-a--erosion, Grade IV-b--ulcer down to subchondral bone, Grade IV-c--eburnation of subchondral bone, Grade V-a--bone...