Table 1 Grading for cartilage, ligaments, bone marrow edema, and subchondral cyst

Cartilage

Grade 0: normal, 1: signal heterogeneity, 2: fraying, 3: fissuring, 4: thinning<50%,

5: thinning>50%, 6: full thickness cartilage loss

Size 1: <10 mm, 2: <20 mm, 3:>20 mm

Ligaments

Grade 0: normal, 1: sprain, 2: partial tear, 3: complete tear

Bone marrow edema

Grade 0: absent, 1: mild (<1 cm), 2: moderate (1–2 cm), 3: severe (>2 cm)

Subchondral cyst

1. Grade the size of each individual subchondral cyst according to the grading templates:

Grade 1: mild (1-3 mm), 2: moderate (>3-6 mm), 3: severe (>6 mm)

2. The sum of individual subchondral cyst grades in each compartment gives total score:

Score 0: no subchondral cyst (0) 1: mild subchondral cysts (1–2) 2: moderate subchondral cysts (3–4) 3: severe subchondral cysts (>5)