Use of Ultrasound for Diagnosis and Follow-Up of Psoriatic Arthritis

Musculoskeletal ultrasound (US) is increasingly used as a bedside tool for diagnostic and monitoring purposes in patients with psoriatic arthritis (PsA). The sonographic differentiation between PsA and rheumatoid arthritis (RA) may be challenging because the morphological appearance of synovitis is similar in both conditions. In contrast, perisynovial inflammation is a specific finding of early PsA, and enthesitis is more frequently detected in PsA than in RA. After initiation of effective therapies, a reduction of US signs of synovitis and enthesitis can be seen along with clinical improvement. A numeric US score for regular monitoring of disease activity and damage in PsA patients has not been established yet. While sonographic findings can be discordant from clinical results, their relevance is unclear, although it is a concern that ongoing subclinical inflammation results in worse structural outcomes. Ongoing studies address the value of sonography as a diagnostic and prognostic marker in PsA, and we expect that these results will emphasise the role of diagnostic US for the routine evaluation of PsA patients.