In the long-term course of rheumatoid arthritis, the hand is afflicted in more than 90% of the cases, but even at first manifestation of the disease the hand is affected at a frequency of almost 40%. It is necessary to reach the diagnosis as quickly as possible to initiate timely therapy. Since early manifestations appear predominantly in damaged soft tissue, plain film radiology usually provides no definitive results. In contrast, sonography not only facilitates detection of soft tissue damage, but also makes it possible to follow the spontaneous course and treatment outcome. The advantages of sonography include feasibility of dynamic examination, lack of side effects, reproducibility, low costs, and almost ubiquitous availability. The disadvantages are the considerable dependence on the examiner and as yet the limited differentiation between effusion and synovitis as well as visualization of the infiltration into the tendon to assess an impending or extant rupture. Based on experience with sonography gathered to date for diagnostic evaluation of inflammatory rheumatic diseases particularly of the hand, it can be stated that especially in the early phases it already provides evidence for inflammatory substrate. Using suitably high-resolution probes ( greater than or equal to 7.5 MHz), it is frequently possible to detect superficial usures and erosions before plain film X-rays which corresponds to the direct arthritic signs in the roentgenogram.
