Over the last few years a sonographic revolution has occurred in rheumatology. Ultrasonography has been shown to be capable of substantially changing the traditional approach to most clinical problems in daily rheumatological practice because of its ability to allow a quick, safe and inexpensive access to otherwise undetectable anatomical information on the early targets of most rheumatic diseases. Ultrasonography completes the physical examination in a rapid and accurate manner and allows the detection of a wide spectrum of pathological findings involving different anatomical structures in the musculoskeletal system. Guidance for intervention (joint aspiration, synovial or soft tissue biopsy, joint or tendon sheath injection) is a major application of ultrasonography. Sonographic guidance is particularly useful when fluid collections are very small or when the inflammatory process is adjacent to anatomical structures that could be seriously damaged by the injection.