Computer tomography (CT) is more sensitive than radiography for detecting structural SIJ changes in the form of erosion of joint facets, joint space alteration and increased bone density (sclerosis). However, CT cannot visualise early active inflammation in the subchondral bone unless using modern Dual-energy CT-technique. Nevertheless, CT can be of help in the diagnosis of minor erosive SIJ changes, which can be difficult to detect by MRI, and in the diagnosis of anatomical variation at the SIJ such as accessory joints. In later stages of the disease, CT can be used to detect spinal changes and is often valuable for the detection and evaluation of spinal fractures.

Additionally, CT can give information for surgery planning, image guided therapy etc.