In the current paradigm for management of patients with rheumatoid arthritis (RA), obtaining clinical remission of symptoms remains the most important aim, but achieving radiographic remission is another key goal of treatment. Several parameters detectable by musculoskeletal ultrasonography can predict the development of severe RA, as well as monitor patients' responses to treatment; thus, musculoskeletal ultrasonography is widely used for evaluating patients with RA, both in clinical trials and in clinical practice. This Review describes the applications of musculoskeletal ultrasonography in patients with RA, focusing on the identification of ultrasonographic features that predict the development of erosions. Such predictive markers include high vascularity of synovitis, persistent synovitis, tenosynovitis of the extensor carpi ulnaris tendon, and erosive changes in the distal ulna. This article also describes ultrasonographic scores that could feasibly be integrated into daily rheumatology practice for the evaluation of patients with RA.