Table 1

Descriptive data for global evaluation of active and structural MRI lesions in the SIJ generated by the majority (four or more) of seven readers from the ASAS MRI group who assessed 278 scans from the ASAS Classification cohort*

VariableNumber (%) of cases
Subchondral BME and meets ASAS definition for positive MRI87 (31.3%)
Subchondral BME112 (40.3%)
Inflammation at site of erosion20 (7.2%)
Capsulitis8 (2.9%)
Joint fluid18 (6.5%)
Enthesitis14 (5.0%)
Subchondral sclerosis40 (16.9%)
Erosion67 (28.3%)
Fat lesion47 (19.8%)
Bone bud1 (0.4%)
Fat metaplasia in an erosion cavity18 (7.6%)
Ankylosis6 (2.5%)
  • *Data for structural lesions available from 238 scans.

  • ASAS, Assessment of SpondyloArthritis international Society; BME, bone marrow oedema; SIJ, sacroiliac joint.