As modern imaging tools such as US and MRI become increasingly available, rheumatologists now have access to highly sensitive measures to assist in the evaluation of both the inflammatory and structural damage components underlying various arthritides over the disease duration. Both US and MRI have associated strengths and weaknesses, and at times they can provide complementary information. This review compares the performance of US vs MRI as diagnostic, prognostic and monitoring tools for RA, and to provide insights into which modality can provide the optimal information for a desired outcome in a given clinical trial or practice situation.