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SIJ - differentials
OCI / postpartum changes
Strain-related SIJ changes
Degenerative / DISH changes
Infectious sacroiliitis
Inflammatory conditions
Metabolic disorders
Spine - differentials
Degenerative changes
Infectious spondylitis

Fractures at the SIJ can occur both in normal and pathological weekend bone, usually located to the sacrum.

Sacral stress fracture may occur in connection with acute minor traumatic injuries and/or overuse injuries in healthy young adults with normal bones doi:10.1016/J.CSM.2005.08.001. Such fractures are difficult to detect by radiography, but MRI will typically display BME within the sacral bone on one or both sides which may be confused with axSpA-related BME if involving the peripheral subchondral areas. However, a fracture line will usually be seen, best on T1-weighted images.


MRI, straight coronal STIR and axial T1 images in a young male after a minor trauma. There is pronounced edema in the sacrum on the left side with a visible fracture line on the T1 images (arrows).

Insufficiency fracture

Sacral insufficiency fracture is more common than stress fracture. It mostly occurs in middle-aged and elderly patients with weakened bone due to e.g., osteoporosis or radiotherapy. The changes by MRI usually consist of pronounced osseous edema, often bilateral with vertical fracture lines, best visualized on T1-weighted images. There may be concomitant transverse sacral fracture, best visualized on sagittal images as showed below; doi:10.1186/S12905-022-01758-2. In doubtful cases, CT can confirm the presence of fracture lines.

MRI in a woman previously receiving radiotherapy due to malignancy, semi-coronal STIR and T1 image with supplementary CT reconstructions. There is pronounced edema in the sacrum on the STIR image with dark intraosseous streaks on the T1-weighted image compatible with insufficiency fractures (arrows). Supplementary CT (images on the right and at the bottom) confirmed the sacral fracture lines (arrows).

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