Ultrasound for enthesitis: handle with care!

Enthesitis, the infl ammation involving the insertion of tendons, ligaments and joint capsule is a characteristic sign and hallmark of several rheumatic diseases in both adult and paediatric patients. The change in the perception of enthesitis (ie, its growing sig-nifi cance as a clinicopathological entity) is best refl ected in the new European League Against Rheumatism (EULAR) recommendations for psoriatic arthritis, which recommend antitumour necrosis factor therapy for patients with active enthesitis and/or dactylitis and insuffi cient response to non-steroidal anti-infl ammatory drugs or local steroid injections. 1 It is also one of three entry criteria (the other two being arthritis and dactylitis) for the new Assessment of SpondyloArthritis Society classifi cation criteria for peripheral spon-dylarthritis. 2 Broadly, enthesitis can be evaluated either clinically or by one of several imaging modalities that have been validated to various extents for the assessment thereof. A recent systematic literature review that examined the US defi nition of enthesi-tis found large variability in the defi nitions utilised to outline enthesitis. 3 Indeed, the appropriate defi nition of enthesitis and of its components remains an issue that is crucial for the evaluation of enthesitis with any given imaging modality. As of yet, we have no single examining modality that is capable of evaluating all of these components. Clinical examination may aid in the detection of enthesitis when palpation is used to trigger pain or tenderness. However, it only allows the detection of soft tissue swelling, including tendon thickening and accompanying bursitis, two key features of enthesitis, while failing to provide information on typical bony changes, ie, bone erosions, enthesophytes and calcifi cations. Clinical evaluation has been shown to underestimate enthesi-tis involvement compared with imaging modalities. 3–6 Contrary to clinical evaluation , conventional radiography is useful for assessing bony changes, as described above, but does not permit the evaluation of soft tissue changes. MRI and ultrasound have clear advantages over both clinical examination and conventional radiography , in that they are capable of providing information with respect to both bony changes and soft tissue processes. MRI is increasingly investigated for its use in assessing enthesitis mainly in anky-losing spondylitis, in which it is capable of detecting diffuse bone oedema associated with surrounding soft tissue oedema in the region adjacent to enthesis. 7 MRI is the imaging modality of choice for assessing bone marrow oedema; however, this may occur in a number of distinct diseases , 8–11 …