Table 3.

Scoring system for assessing structural damage of the sacroiliac joint by MRI according to the JAMRIS-SIJ scoring system.

Item	Definition	Score
		Segmentation/Slice	Range/Slice
Sclerosis	A substantially wider than normal area of very low bone marrow signal intensity within the subchondral bone in the ilium or sacrum on a nonfat suppressed sequence, preferably a nonfat suppressed T1-weighted sequence; this feature must also be present on all other sequences, as available	4 quadrants/SIJ	0–8
Erosions	A focal loss of low signal of cortical bone at osteochondral interface and adjacent marrow matrix on T1-weighted images	4 quadrants/SIJ	0–8
Fat lesion/Fat metaplasia	Homogeneous increased signal intensity within subchondral bone marrow on T1-weighted images	4 quadrants/SIJ	0–8
Backfill	A high signal on non-contrast-enhanced T1-weighted sequences in a typical location for erosion, with signal intensity greater than normal bone marrow, clearly demarcated from adjacent bone marrow by an irregular band of low signal, reflecting sclerosis at border of original erosion	halves/SIJ	0–4
Ankylosis	Presence of signal equivalent to regional bone marrow continuously bridging a portion of the joint space between iliac and sacral bones	halves/SIJ	0–4