Objective To compare the ultrasonic features of enthesitis between psoriatic arthritis and psoriasis vulgaris. Methods A total of 39 patients with psoriatic arthritis (PsA group), 60 with psoriasis vulgaris (non-PsA group) and 60 healthy people (control group) participated in this study. They were examined by two-dimensional and color Doppler ultrasound on the entheses of bilateral femoral quadriceps tendons, patella tendons, Achilles tendons, plantar fasciae, common flexor tendons and common extensor tendons. Results About 45% (27 cases) healthy controls had enthesitis, with Achilles tendons and femoral quadriceps tendons being most likely affected. No blood flow signal was observed on the affected sites. About 63% (38 cases) of non-PsA patients had enthesitis, with Achilles tendons and femoral quadriceps tendons being most likely affected. Blood flow signals were observed on 4 affected sites. More than 84% (33 cases) PsA patients had enthesitis, with all locations being likely affected but mostly on Achilles tendons, femoral quadriceps tendons, and plantar fasciae. Blood flow signals were observed on 18 affected sites. The differences in prevalence of enthesitis were statistically significant (PsA group>non-PsA group>control group, all PPP
