Ultrasound of the Foot and Ankle in Peripheral Spondyloarthritis

Seronegative spondyloarthritis (SpA) is an umbrella term that includes ankylosing spondylitis (AS), psoriatic arthritis, reactive arthritis, and arthritis related to inflammatory bowel disease. Apart from AS, these other conditions predominantly affect the appendicular skeleton. Both the foot and ankle are frequently involved peripheral joints. According to the latest Assessment of Spondyloarthritis International Society criteria, imaging is a key way to diagnose peripheral seronegative SpA. Common imaging features are enthesitis, synovitis, tenosynovitis, erosive and bone-proliferative changes in the affected joints, and effusion.Although magnetic resonance imaging is the gold standard technique, ultrasound (US) is a cost-effective imaging method that can readily detect the features just described. Additionally, it can semi-quantify inflammatory changes, helping in treatment and dose modifications. Imaging-guided procedures, such as biopsies and steroid injections, are routinely performed using US. Furthermore, US can easily be deployed at outpatient rheumatology clinics, making it an ideal point-of-care investigation.