Ultrasound imaging in psoriatic arthritis and ankylosing spondylitis.

Musculoskeletal ultrasound (US) is a reliable imaging technique which has a key role in the assessment of patients with psoriatic arthritis (PsA) and ankylosing spondylitis (AS). US can help in the diagnosis of the disorder, in the evaluation of the extent of the joint and enthesis involvement and in therapy monitoring because it can reflect both morphostructural changes and inflammatory activity. Several studies have reported that US revealed pathological findings at joints and enthesis in a large number of PsA patients who do not complain of active pain and/or swelling at the time of the clinical examination and in psoriasis patients with no signs of musculoskeletal disease. The application of US in the evaluation of nail and skin involvement in patients affected by psoriasis, with or without arthritis, and the imaging of sacroiliac joints is an interesting approach. US has already become commonplace in both clinical and research fields, and improvements in US technology will offer further possibilities for future research.