Musculoskeletal ultrasound (US) has an increasingly important role in the assessment of spondyloarthritis (SpA) not only for its ability to detect synovial and tendon involvement but also for the accurate imaging of enthesitis, the clinical hallmark feature of SpA. As already known, most cases of enthesitis are subclinical in SpA and US is an effective technique used to detect them. Also, in cases of dactylitis, US can accurately delineate the underlying pathology. US allows clinicians to guide needle positioning within inflamed joints, tendon sheaths and entheses in order to inject steroids or other drugs. This is particularly important for patients with SpA, because of the frequency of mono or oligoarthritis, tendon and entheseal involvement, who may have great benefit from intrarticular or intralesional therapy. The clinical application of US in SpA extends to the monitoring of therapy efficacy, particularly when coupled with power Doppler imaging. Very slight changes in vascularity are easily detected in joints, entheses or tendons, aiding the rheumatologist in the assessment of the effects of local or systemic therapies. The present review provides an update of the available data and discusses research issues of US imaging in SpA.