This lecture focuses on MRI evaluation of the sacroiliac (SI) joints in children with suspected juvenile spondyloarthritis. The session highlights important differences between pediatric and adult disease, reviews appropriate MRI protocols, and discusses the imaging features of sacroiliitis in the growing skeleton. Particular emphasis is placed on common developmental variants and pitfalls that can mimic inflammation, helping radiologists avoid overcalling disease and improve diagnostic accuracy in pediatric patients.

Learning Objectives

By the end of this lecture, participants will be able to:

• Describe the role of MRI in the assessment of juvenile spondyloarthritis and sacroiliitis.
• Recognize the key MRI findings of active sacroiliitis in children, including bone marrow edema and inflammatory lesions.
• Understand how pediatric sacroiliac joint anatomy and development differ from adults and influence image interpretation.
• Identify common normal variants and imaging pitfalls, such as sacral flaring, physiologic joint fluid, and vascular channels.
• Appreciate the limitations of T1-weighted imaging for assessing erosions in children and apply appropriate interpretation strategies.
• Incorporate optimized MRI protocols and advanced sequences into routine pediatric SI joint imaging.