The Role of Ultrasound in Psoriatic Arthritis — Do We Need a Score?

Enthesitis is one of the hallmarks of the spondyloarthritis (SpA) group, including psoriatic arthritis (PsA)1,2. Enthesitis is usually defined as inflammation at the site of attachment of a tendon, ligament, and capsule onto bone, which can cause significant pain and disability for patients2. In recent years, the interest in this domain of disease has grown with increasing evidence of its prevalence and potential importance in the pathogenesis of the disease3. One of the limitations in understanding the exact role of enthesitis in these diseases has been the difficulty in assessing this feature3,4. Usually enthesitis is evaluated by clinical assessment, which measured the pain provoked by physical examination of entheseal sites. However, tenderness at the entheseal site does not always denote inflammation, and its absence does not rule out enthesitis. The introduction of new drugs and the wider use of imaging, especially magnetic resonance imaging and ultrasound (US) in clinical and research practice, highlight the pivotal role of enthesitis for the diagnosis and management of both SpA (axial and peripheral) and PsA. Nevertheless, it has frequently been shown that clinical assessment of pain at tendon insertions does not always correlate with imaging assessment of inflammation5,6,7,8. The clinical examination of enthesitis may also identify pain from tendinosis, from nearby joint synovitis, or from other pain mechanisms without any true involvement of the adjacent enthesis. In addition, it has been reported that a significant proportion of patients with PsA, and indeed patients with psoriasis, have subclinical enthesitis with inflammation seen on imaging, without tenderness at the insertion9. US has been proven to be a valuable tool to assess entheseal involvement across the SpA spectrum, including PsA7,8,9 … Address correspondence to L.C. Coates, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, Windmill Road, Oxford OX3 7LD, UK. E-mail: laura.coates{at}ndorms.ox.ac.uk.