To compare the efficacy of ultrasound-guided intra-articular (IA) treatment with platelet-rich plasma (PRP) versus viscosupplementation (hyaluronic acid HA) in hip osteoarthritis. METHODS: A total of 43 patients affected by monolateral severe hip osteoarthritis (OA) were included in the study. Patients were randomized to receive either intra-articular PRP (3 ml) or HA (30 mg/2 ml; 1,000-2,900 kDa), 3 injections in total - 1/week. Clinical assessments for each patient were made at baseline (T0), 4 (T1), and 16 weeks (T2) of follow-up. The primary efficacy outcome was pain reduction as measured by VAS and by WOMAC pain subscale.