111 patients with Kellgren-Lawrence grade I-IV symptomatic knee osteoarthritis were randomized to three weekly intraarticular injections of either leukocyte-poor platelet-rich plasma (LP-PRP) or hyaluronic acid. Patients were assessed for pain and function over a 52-week follow-up. The primary outcome measure, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score, demonstrated no significant difference between groups at any time point. In contrast, pain scores on a visual analog scale (VAS) demonstrated significantly lower pain in the LP-PRP group compared to the HA group at 24- and 52-week follow-up. Similarly International Knee Documentation Committee (IKDC) subjective scores were significantly greater in the LP-PRP group compared to the HA group at 24 and 52 weeks.