In this episode of RheumaCast, we explore how anatomical variations of the sacroiliac joints (SIJ) can complicate the diagnosis and management of axial spondyloarthritis (axSpA). We walk you through common SIJ variants—such as crescent-shaped ilium, accessory joints, and transitional vertebrae—and explain how these can mimic sacroiliitis on MRI.

We discuss how to differentiate true inflammation from mechanical stress reactions, when to use CT for clarification, and the implications of these findings for diagnosis, treatment, and research. If you’ve ever wondered how much “background noise” anatomy adds to SIJ imaging, this episode is for you.

This episode is based on the publication: Diekhoff T and Ziegeler K. Curr Opin Rheumatol 2025 and developed with NotebookLM.