Do you recommend the use of contrast to identify sacroiliitis on MRI?

If axial spondyloarthritis is suspected, and Xray of pelvis is either normal or equivocal then an MRI of SI joints is ordered to support the diagnosis of axial spondyloarthritis. The recommendation by ASAS is to order 2 sequences, T1-fat enhancing sequence, and a STIR- fat suppression sequence without contrast.

The change suggestive of osteitis on MRI of SI joints is bone marrow oedema [BMO]. BMO is depicted as a hyperintense signal on short tau inversion recovery (STIR) images (or equivalent water-sensitive sequences) and usually as a hypointense signal on T1-weighted images (figure 1). The more intense the signal the more likely that it reflects active inflammation.

Additionally, the T1 weighted image may show erosions or structural damage ...

Agree with the above. There are several studies showing no additional benefit of contrast to identify sacroiliitis.