The administration of disease-modifying antirheumatic drugs (DMARDs) in the early period of rheumatoid arthritis (RA) is critical for protecting against joint damage and inducing remission. Physicians need to identify patients at risk of progression to RA at the early stages of arthritis. Musculoskeletal ultrasonography (MSUS) allows the direct visualization of synovitis and bone erosion in the early phase, and may be useful for differentiating early rheumatoid arthritis from other inflammatory arthritis. Power Doppler sonography is a promising tool for assessing the disease activity and monitoring the effects of DMARDs. This article reviews the current status and recent advances in MSUS imaging in RA.