The use of ultrasound for the assessment of enthesitis in patients with spondyloarthritis.

Seronegative spondyloarthritis (SpA) represents a group of diseases that share certain genetic, clinical, and radiographic features. Enthesitis, inflammation at the site of tendon insertion into the bone, involving both the axial and the peripheral joints, is an important sign of SpA. Clinical diagnosis of enthesitis, however, is neither sensitive nor specific; thus, the diagnosis of enthesitis often relies on typical abnormalities in imaging studies. Due to its low costs and availability, ultrasound is emerging as the preferred technique for detection of enthesitis for both clinical and research purposes. Ultrasonographic features of enthesitis include tendon hypoechogenicity and thickening, calcifications, bone erosions, and Doppler signal. Several semi-quantitative scoring systems have been developed to quantify ultrasonographic abnormalities of the entheses. These methods have been used for early diagnosis and classification of SpA as well as for monitoring response to treatment.