US definition of enthesitis in SpA and PsA was proposed by the OMERACT group: ‘hypoechoic and/or thickened insertion of the tendon close to the bone (within 2 mm from the bony cortex), which exhibits Doppler signal if active and which may show erosions and enthesophytes/calcifications as a sign of structural damage.
Only Doppler mode can assess whether an enthesitis is active or not, but the presence of Doppler signal without B-mode findings (i.e. hypoechogenicity and thickening) is apparently not sufficient to define enthesitis.
Thus, the presence of Doppler signal alone (ie, without hypoechoic areas or entheseal thickening) should also be regarded as sufficient to define enthesitis, and not only to state its ‘activity’