Ultrasound and its clinical use in rheumatoid arthritis: where do we stand?

High-resolution musculoskeletal ultrasound (MSUS) has been increasingly employed in daily rheumatological practice and in clinical research. In rheumatoid arthritis (RA), MSUS can be now considered a complement to physical examination. This method evaluates synovitis through gray-scale and power Doppler and it is also able to identify bone erosions. The utilization of MSUS as a marker of RA activity has received attention in recent literature. Current data account for good correlation of MSUS with classical measures of clinical activity; in some instances, MSUS appears to perform even better. Diagnosis of subclinical synovitis by MSUS might help the physician in RA management. With some variation, interobserver MSUS agreement seems excellent for erosion and good for synovitis. However, lack of MSUS score standardization is still an unmet need. In this review, we describe several MSUS scores, as well as their correlation with clinical RA activity and response to therapy. Finally, we look at the relationship of MSUS with synovial tissue inflammation and discuss future perspectives for a better interpretation and integration of this imaging method into clinical practice.