Table 1.

Grading of MRI-synovial inflammatory markers

MRI-inflammatory markers	Criteria
Effusion-synovitis according to ACLOAS	Anteroposterior diameter of joint distension on the mid-slice sagittal image
0	< 2 mm
1	≥ 2 to < 5 mm
2	≥ 5 and < 10 mm
3	≥ 10 mm
Effusion-synovitis according to MOAKS	Graded on axial image
0	Physiologic amount of fluid
1	Small amount of fluid continuously extending into the retropatellar space
2	Medium - with slight convexity of the suprapatellar bursa
3	Large - evidence of capsular distention
Infrapatellar fat pad (IPFP) abnormality	Hyperintense signal intensity in IPFP on IW fat-suppressed images
The size of IPFP abnormality
0	No signal abnormality
1	≤ 33% of the region
2	34 – 66% of the region
3	≥ 66% of the region
The highest signal intensity in IPFP abnormality
0	None
1	Mild (lower than cartilage)
2	Moderate (equal to or higher than cartilage but lower than fluid)
3	Severe (equal to fluid)
Synovial proliferation score in kneea and popliteal cystb	Graded on fat-saturated DESS and IW images
1	Smooth synovium, with no proliferation or synovial bands visible
2	Mild irregularity of the synovium, either focal or diffuse, and the presence of some synovial bands or small bodies
3	Extensive synovial thickening with irregular villonodular proliferation

^aIf the synovitis-effusion score was ≥ 1 by either ACLOAS or MOAKS methods

^bUsed only in knees with a popliteal cyst

ACLOAS, Anterior Cruciate Ligament OsteoArthritis Score; MOAKS, MRI Osteoarthritis Knee Score; IW, Intermediate-Weighted sequence