where it was always detected at the cortical bone insertion and sometimes also in the bursa. In SpA patients, the US pattern depended on the clinical presentation, with a higher prevalence of the most severe stages in those with peripheral forms.Conclusion. US in B mode combined with power Doppler allowed the detection of peripheral enthesitis in a majority of SpA patients, but not in MBP or RA patients. The presence of entheseal involvement was independent of SpA subtype, but its degree of severity appeared to be greater in peripheral forms. US could be very useful for both the diagnosis and the assessment of SpA activity.