Diagnostic imaging of psoriatic arthritis. Part II: magnetic resonance imaging and ultrasonography.

Plain radiography reveals specific, yet late changes of advanced psoriatic arthritis. Early inflammatory changes are seen both on magnetic resonance imaging and ultrasound within peripheral joints (arthritis, synovitis), tendons sheaths (tenosynovitis, tendovaginitis) and entheses (enthesitis, enthesopathy). In addition, magnetic resonance imaging enables the assessment of inflammatory features in the sacroiliac joints (sacroiliitis), and the spine (spondylitis). In this article, we review current opinions on the diagnostics of some selective, and distinctive features of psoriatic arthritis concerning magnetic resonance imaging and ultrasound and present some hypotheses on psoriatic arthritis etiopathogenesis, which have been studied with the use of magnetic resonance imaging. The following elements of the psoriatic arthritis are discussed: enthesitis, extracapsular inflammation, dactylitis, distal interphalangeal joint and nail disease, and the ability of magnetic resonance imaging to differentiate undifferentiated arthritis, the value of whole-body magnetic resonance imaging and dynamic contrast-enhanced magnetic resonance imaging.