1.X-ray grading: grading according to Kellgren-Lawrence (K-L) grading standard Grade 0: normal; Grade I: no narrowing of the joint space, suspicious bone redundancy or micro bone redundancy; Grade II: suspicious narrowing of the joint space, obvious mild bone redundancy; Grade III: obvious narrowing of the joint space, sclerotic changes of the bone, moderate multiple bone redundancy formation; Grade IV: obvious narrowing of the joint space, serious sclerotic changes and obvious joint deformity, large bone redundancy formation. Severe sclerotic changes and obvious joint deformity, with a large amount of bone superfluous formation. 2, arthroscopic grading (1) Outerbridge grading I degree: mild surface blisters (softening and swelling); II degree: gross and superficial ulceration and fibrosis less than 1 cm in diameter; III degree: damage diameter greater than 1 cm deep ulceration, no subchondral bone exposure; IV degree: full-thickness tear combined with subchondral bone exposure. (2) International Cartilage Repair Society cartilage injury grading system (ICRS) Degree I: superficial, blunt notch and superficial dehiscence; Degree II: injury < half of cartilage thickness; Degree III: injury ≥ half of cartilage thickness but not reaching subchondral bone; Degree IV: full-thickness tear combined with subchondral bone exposure.