Abstract  The apparent incidence of iliopsoas muscle abnormalities is currently rapidly increasing secondary to the increased number of immuno-compromised patients, malignancies, chemotherapy, immunotherapy, multi-systemic disease and the wide availability of cross-sectional imaging. Disease of the iliopsoas compartment can present with non-specific or indolent clinical features, particularly where normal immune responses are attenuated. Delay in diagnosis can lead to inappropriate initial treatment and, in some cases, serious complications. Wider availability and application of modern cross-sectional imaging offers rapid, confident diagnosis. An understanding of iliopsoas compartment anatomy and pathways of disease spread are essential to recognising these clinically important conditions. We review the anatomy, clinical presentation and common imaging findings of iliopsoas disease as it presents through the emergency room.