Musculoskeletal sonography (MSUS) has played a growing role in the diagnosis and management of rheumatic diseases, enabling the imaging of synovitis, bone erosion, and cartilage damage in the early phase of arthritis. "Dynamic" evaluation of tendons and help in guiding needle positioning in interventional manoeuvres are some of the other reasons for its success. MSUS, particularly when coupled with power Doppler (PD) examination, has recently been shown to be an efficient tool for monitoring disease activity and progression in rheumatoid arthritis, spondyloarthritis, crystal-related arthropathy, and osteoarthritis, with general consensus on its interesting results. More specifically, the PD signal has proved to be a simple and promising tool for short-term monitoring of synovial vascularity changes induced by steroids or biological agents in RA patients. MSUS has some limits, because of the physical properties of US and the quality of the equipment; it is, moreover, an operator-related imaging technique, with few standardized protocols. Future goals should be standardization of the examining approach in grey scale and Doppler ultrasound (US), including use of new equipment (3D US), extensive use in other fields (i.e. connective tissue diseases and vasculitis), and possible new applications (e.g. thoracic US).