INTRODUCTION

Ultrasonography (US), sometimes referred to as ultrasound imaging or sonography, is an imaging modality that utilizes reflected pulses of high frequency (ultrasonic) sound waves to assess soft tissues, cartilage, bone surfaces, and fluid containing structures. Ultrasonographic imaging, once the sole province of radiologists, is becoming more widely available in rheumatology clinics and in other ambulatory and emergency settings. However, the widespread use of US by clinicians who diagnose and treat musculoskeletal disorders has been hampered by questions related to the reliability, validity, standardization, methodology, and the ability to detect changes over time. Technical aspects of musculoskeletal ultrasonography, the validity and reliability of image acquisition, and interpretation in rheumatic disorders, primarily in patients with rheumatoid arthritis, are addressed in detail separately. (See "Musculoskeletal ultrasonography: Nomenclature, technical considerations, validation, and standardization".)

The use of ultrasonography to assess patients with rheumatic diseases in the clinic was fostered by the development of compact real-time US systems in the 1980s. Synovitis of the knee was the earliest musculoskeletal disorder assessed ultrasonographically in the clinic [1]. Ultrasonographic assessment of synovitis of the small joints of the hands in patients with rheumatoid arthritis followed by a decade [2], aided by the availability in the 1990s of high-resolution transducers that made detailed assessment of superficial structures feasible.

Selected clinical applications of musculoskeletal ultrasonography are discussed here. An overview of imaging modalities and guidelines for selecting imaging studies (eg, plain film radiography, computed x-ray tomography [CT scan], magnetic resonance imaging [MRI], and ultrasonography) for musculoskeletal problems are presented separately. (See "Imaging techniques for evaluation of the painful joint" and "Radiologic evaluation of the painful hip in adults" and "Radiologic evaluation of the painful shoulder".)

Diagnostic imaging is only one element in the assessment of patients with musculoskeletal symptoms. The clinical approach to such patients, including, in most instances, suggestions regarding the role of diagnostic imaging in their assessment, is discussed in the topics that deal with the initial evaluation of patients presenting with pain in various parts of the body. Examples include shoulder pain, hip pain, and knee pain. (See "Evaluation of the patient with shoulder complaints" and "Evaluation of the adult with hip pain" and "Evaluation of the active adult patient with knee pain".)

ACQUIRING IMAGES

For the musculoskeletal ultrasonographer, the selection of anatomic structures to image and the planes in which two-dimensional ultrasonography is performed is primarily complaint-driven. Standardized scans and disease-specific protocols for imaging are alternative approaches that are used in certain settings.