The Role of Musculoskeletal Ultrasound in the Rheumatoid Arthritis Continuum

Abstract

Purpose of review: Rheumatoid arthritis (RA) is no longer considered a fixed phenotype but rather a disease continuum. This review outlines the current and potential value of applying ultrasound (US) along this continuum: from the prediction of progression to RA in at-risk individuals, to confirmation of the early diagnosis of RA, as well as the consideration of differential diagnoses, and the use in disease monitoring and defining remission.

Recent findings: In individuals at-risk of RA (i.e., positive autoantibodies with symptoms but without synovitis), US has shown a promising predictive value for the development of clinical arthritis, providing the opportunity to improve risk stratification (and disease prevention) of these individuals. The detection of inflammation on US in patients with early undifferentiated arthritis, in which a definite diagnosis cannot be reached, could predict evolution to persistent arthritis, mostly RA. This, in addition to the US potential ability to identify disease specific patterns for different rheumatic conditions, might facilitate early diagnosis and, therefore, improve the management of patients with RA, or other types of inflammatory arthritides. US has also demonstrated the capability to predict radiographic progression, and relapse risk after treatment discontinuation, in RA patients in remission according to the clinical instruments, raising implications in the management, including therapy discontinuation, of these patients. US has an undeniable value in the management of patients at different stages along the RA continuum. Further research is needed to identify which groups of patients benefit the most from US imaging.

Keywords: Differential diagnosis; Disease monitoring; Musculoskeletal ultrasound; Remission; Rheumatoid arthritis.

Fig. 1

Tenosynovitis of the third flexor digitorum tendons in a patient with rheumatoid arthritis. The longitudinal scan of the flexor digitorum tendons shows the presence of synovial hypertrophy (asterisks) and synovial effusion (rounded dots) in the synovial tendon sheath. Legend: fdt, flexor digitorum tendons

Fig. 2

Bone erosion in the second metacarpophalangeal joint in a patient with rheumatoid arthritis. Longitudinal scan. The callipers point out a small bone erosion (size 0.77 mm) in the metacarpal head. Legend: asterisks, synovial hypertrophy; et, extensor tendon; mh, metacarpal head; p, proximal phalanx

Fig. 3

The potential uses of ultrasound in the rheumatoid arthritis continuum. The figure illustrates the potential value of US in the management of patients at different stages along the RA continuum: in individuals at risk of RA, the detection of subclinical synovitis and structural damage has shown to improve prediction of clinical arthritis, thus informing risk stratification and management of these individuals. US has also shown a promising role in the identification of patients with undifferentiated arthritis who will develop RA, with potential implications on early diagnosis and management of these patients (‘window of opportunity’). In RA patients with established disease, in clinical remission according to the clinical instrument (i.e., DAS 28), the detection subclinical inflammation has been shown to predict progression to structural damage and disease relapse after tapering of the treatment. In this context, US has a promising role in guiding the management of these patients, including treatment discontinuation, in addition to the routinely used clinical instruments. Legend: Ab, antibodies; DAS, disease activity score; PD, power Doppler; MSK, musculoskeletal; RA, rheumatoid arthritis; US, ultrasound

Fig. 4

“Double contour sign” and a large bone erosion in the second metacarpophalangeal joint in a patient with gout. Longitudinal scan. The US image shows the presence of the “double contour sign” (arrowheads) over the hyaline cartilage, as well as the presence of a large extra-articular bone erosion filled with hyperechoic spots (arrows) indicating monosodium urate crystal deposits. Legend: et, extensor tendon; mh, metacarpal head; p, proximal phalanx