Spondylarthritis (SPA) are the second most frequent inflammatory rheumatic disorders and, because it starts early in life and has a chronic progressive course, the impact of this disease on health resources and patient's life quality can be important. Because the characteritic signs of SPA, like radiological evidence of sacro-iliitis, appear late in time, the lag time between the onset first signs of SPA for the patient and the confirmed diagnosis can be very long (up to 8 years). Previous studies proved that patients who are affected by SPA are showing abnormal vascularization of peripheral enthesis more frequently than patients affected by other rheumatic diseases. Ultrasonography in B mode combined with power Doppler (PDUS) is a non invasive and highly sensitive toll which can detect enthesitis and abnormal vsacularization even for the patients who are not showing yet the evidence of SPA's symptomatology. Using PDUS as a early diagnosis tool could lead to the improvement of diagnostic procedures and therapeutic management of SpA and reduce the cost of diagnosis for patient and health insurances.