As a research tool, medical imaging has considerably increased our understanding of joint inflammation in vivo. Although conventional radiography remains important for diagnosis, other imaging modalities such as magnetic resonance imaging (MRI) and ultrasonography show considerable potential for the study of joint inflammation in the research setting. The advances in MRI and ultrasound in the last decade has lead to significant conceptual advances into the microanatomical basis for arthritis. The purpose of this chapter is to describe how MRI and ultrasound can be used in the research environment. Other imaging techniques such as computed tomography and scintigraphy have little use in studying inflamed synovial joints due to their relative inability to demonstrate inflammation, or poor resolution or both. However, molecular imaging using high-resolution positron emission tomography or single photon emission computed tomography is being increasingly used to study inflammation in the experimental setting and also in man.