Ultrasound in rheumatic and musculoskeletal diseases: From musculoskeletal to organ involvement

In last two decades, the use of ultrasound has assumed an increasingly important role in the assessment of almost all rheumatic and musculoskeletal diseases. Over the years, much advancement has been made in the sonographic evaluation of articular and periarticular structures, validating definitions of normal sonographic appearance of various types of tissues and structures as well as elementary sonographic lesions and scoring systems to apply in the detection and monitoring of inflammatory and structural lesions. Since extra-articular involvement is very common in rheumatic and musculoskeletal diseases, there is growing interest and evidence on how ultrasound can be applied to the examination of different tissues and organs beyond synovial joints. In this narrative review, we will provide an overview of the available data on the use of ultrasound in the musculoskeletal system (joint, tendon, enthesis, muscle) and extra-articular organs (cardiovascular system, salivary and lacrimal gland, lung, skin and nails), including elementary lesions, scoring systems and their relevance to diagnosis, monitoring, prediction and assessing treatment efficacy in rheumatic and musculoskeletal diseases.