This report presents the results of a recent systematic review performed by the OMERACT Ultrasound Group on the metric properties of ultrasound for the detection of synovitis in inflammatory arthritis. Reviews were conducted for the hand, wrist, elbow, shoulder, knee, ankle, and foot; most reports were related to the hand and knee, and the most common disease process was rheumatoid arthritis. The review highlights the current gaps in the literature, including a lack of reliability data with respect to intra-occasion and intra- and inter-reader reliability. Current work by our group is addressing these issues.