Anatomical variation of the sacroiliac joints - what the rheumatologist should know.

PURPOSE OF REVIEW: Anatomical variations of the sacroiliac joints (SIJ) pose challenges in the diagnosis of axial spondyloarthritis (axSpA). Increased reliance on magnetic resonance imaging (MRI) for early detection has led to concerns about specificity, as anatomical variants can mimic inflammatory changes. This review highlights common SIJ variations and their implications for rheumatologists interpreting imaging findings.

RECENT FINDINGS: Recent studies emphasize the high prevalence of SIJ anatomical variations, particularly in females, and their potential to influence imaging interpretation. Variations such as crescent-shaped ileum, intraarticular dysmorphisms, and accessory joint facets can lead to bone marrow edema and sclerosis, mimicking sacroiliitis. Additionally, lumbosacral transitional vertebrae alter SIJ biomechanics, potentially exacerbating symptoms in axSpA patients. Advances in MRI and computed tomography (CT) imaging protocols provide improved differentiation between anatomical variants and true inflammatory changes.

SUMMARY: Recognizing SIJ anatomical variations is crucial for avoiding misinterpretation of imaging findings and overdiagnosis of axSpA. MRI protocols incorporating additional imaging planes and CT correlation can enhance diagnostic accuracy. Awareness of these variations can refine patient management strategies, ensuring appropriate treatment for inflammatory and biomechanical SIJ pathologies.