Fig. 1

Sample slice and scoring methods for sacroiliac joint inflammation score (SIS). a Coronal oblique short-tau inversion recovery (STIR) image of the sacroiliac joints shows each joint divided into four quadrants. There is normal bright subchondral signal along both sides of the right sacroiliac joint and along the periarticular region of the left sacrum (solid arrows) in this skeletally immature patient. On the left, there is abnormal signal consistent with bone marrow edema within the periarticular region of the left ilium in both the upper and lower quadrants (dashed arrows). b Scoring schematic demonstrates a “1” within the left iliac bone in both the upper and lower quadrants representing bone marrow edema. An additional score of “1” is given as the depth of the bone marrow edema extends > 1 cm from the articular surface. The patient received a total score of “3” for this image slice