Imaging the patient with sacroiliac pain

Sacroiliac (SI) region pain is a common clinical presentation and is often due to pathology involving the SI joints, usually of inflammatory, infective, neoplastic, or post-traumatic etiology. The SI joints have a unique anatomic layout and composition and can be imaged with a variety of techniques including conventional radiographs, computed tomography, isotope bone scintigraphy, and magnetic resonance imaging. This article reviews a range of common SI joint conditions, illustrated by multimodality imaging findings. We also discuss strategies for choosing the optimal imaging modality, pearls, and pitfalls of imaging and discuss an algorithm for approaching the patient with suspected inflammatory back pain.