Feature | Definition |
---|---|
Inflammation MRI components | |
BME | An ill-defined area of high bone marrow signal intensity† on fluid-sensitive sequences within the subchondral bone of the ilium or sacrum |
Joint space inflammation | Increased signal intensity on fluid sensitive and/or contrast-enhanced T1-weighted images within the joint space of the cartilaginous portion of the SIJ |
Capsulitis | Increased signal intensity on fluid sensitive and/or contrast-enhanced T1-weighted images involving the SIJ capsule |
Enthesitis | Increased signal intensity within the bone marrow and/or adjacent soft tissue on fluid sensitive and/or contrast-enhanced T1-weighted images at sites where ligaments and tendons attach to a bone |
Structural MRI components | |
Sclerosis | A substantially wider than normal (of ≥ 5 mm in adolescents) area of low subarticular bone signal on T1-weighted and fluid sensitive images |
Erosion | Bony defect (or irregularity with associated BME, sclerosis, or fatty lesion) at the osteochondral interface involving the bone contour and presenting with low signal intensity on T1-weighted and fluid-sensitive images |
Fatty lesion | Homogeneous increased signal intensity within the subchondral bone on T1-weighted non-FS image presenting with a distinct border of the lesion |
Ankylosis | Presence of signal equivalent to regional bone marrow continuously bridging a portion of the joint space between the iliac and sacral bones |
Statement of overarching consideration for all definitions: “[…] in comparison to physiological changes normally seen on MRI examinations of age- and sex-matched children, and visible in 2 planes wherever available.”
↵† Caveat for BME: “[…] compared to the signal intensity of the iliac crest, edges of the vertebrae, and triradiate cartilage wherever available.” JAMRIS-SIJ: Juvenile Arthritis Magnetic Resonance Image Sacroiliac Joint Scoring System; MRI: magnetic resonance imaging; BME: bone marrow edema; SIJ: sacroiliac joint; FS: fat suppressed.