This review highlights the increasing evidence from the last few years supporting the use of musculoskeletal ultrasonography (MSUS) in the evaluation and management of patients with pediatric rheumatic diseases, particularly focusing on juvenile idiopathic arthritis. Recently developed definitions for the sonographic appearance of healthy and pathologic joints in children are discussed. Further topics explored include how MSUS enhances the diagnosis of inflammatory joint disease (synovitis, enthesitis, tenosynovitis), including the detection of subclinical synovitis. There is a brief summary on the use of ultrasonography in the evaluations of myositis, Sjögren syndrome, and scleroderma.