Ultrasound in rheumatology

Role

Musculoskeletal ultrasound provides real-time, dynamic, radiation-free assessment of synovitis, tenosynovitis, effusion, and soft tissue pathology - increasingly used as a bedside extension of the clinical examination in rheumatology practice, alongside guiding procedures
Growing rapidly in rheumatology practice given its accessibility, lack of radiation, and ability to detect subclinical synovitis not apparent on clinical examination alone

Doppler ultrasound specifically detects increased blood flow associated with active synovial inflammation, distinguishing active synovitis (Doppler-positive) from inactive/residual synovial thickening (Doppler-negative) - a distinction clinical examination alone cannot reliably make

Detects synovitis and erosions more sensitively than clinical examination and earlier than plain X-ray, similar in principle to MRI's advantage, though ultrasound cannot assess bone marrow oedema (an MRI-specific finding)
Used to guide accurate joint/soft tissue injection and aspiration (particularly for smaller or technically difficult joints), improving procedural accuracy compared with a landmark-based (blind) technique

Findings of subclinical Doppler-positive synovitis (inflammation detected on ultrasound despite apparent clinical remission) can inform treatment intensification decisions in some treat-to-target protocols, reflecting evidence that subclinical inflammation predicts subsequent relapse/damage
Highly operator-dependent - image quality and interpretation reliability depend substantially on operator training/experience, more so than for many other imaging modalities

Rheumatoid arthritis remission assessment (subclinical synovitis detection), ultrasound-guided joint injection/aspiration, tenosynovitis, crystal arthropathy (double contour sign in gout)

Ultrasound-detected subclinical synovitis in a patient otherwise judged to be in clinical remission is a recognised predictor of subsequent flare/structural progression - raising the question (still being actively studied) of whether treatment decisions should incorporate ultrasound findings alongside standard clinical disease activity measures

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