Intra-articular injections of platelet-rich plasma (PRP) and hyaluronic acid (HA) represent efficacious medical treatments for osteoarthritis (OA), although no comparative study on long-term efficacy in hip OA exists. The goals of the current study were to compare the clinical efficacy of PRP vs HA at 12 months of follow-up in patients with hip OA and evaluate the influence of the type of infiltration and patient age, sex, body mass index, and degree of OA on temporal clinical evolution. One hundred patients with chronic unilateral symptomatic hip OA were consecutively enrolled and randomly assigned to 1 of 2 groups: group A received PRP and group B received HA administered via intra-articular ultrasound-guided injections. Patients were evaluated at baseline and after 1, 3, 6, and 12 months using the Harris Hip Score (HHS) and visual analog scale (VAS). An overall improvement was detected in both groups between 1- and 3-month follow-up. Despite a slightly progressive worsening between 6- and 12-month follow-up, the final clinical scores remained higher compared with baseline (P<.0005), with no significant differences between PRP and HA. Regarding clinical temporal evolution, multivariate analysis showed that HHS was not influenced by the type of infiltration, patient age, sex, body mass index, or degree of OA, whereas a significant association was detected between OA grade IV and VAS evolution (P<.0005). Intra-articular injections of PRP are efficacious in terms of functional improvement and pain reduction but are not superior to HA in patients with symptomatic hip OA at 12-month follow-up.