[Cross-sectional imaging of peripheral involvement in psoriatic arthritis].

The purpose of this article is to: 1) describe the main plain film, ultrasound and MR imaging features of peripheral involvement in psoriatic arthritis, 2) describe the advantages of ultrasound and MRI at the early stages of the disease; 3) describe how to use MRI and ultrasound in order to assess response to tumor necrosis factor-alpha blocker therapy.