192 patients with knee osteoarthritis were randomized to three weekly intraarticular injections with either platelet-rich plasma or hyaluronic acid. The focuse of the current study was outcome after 2 and 5 years following treatment. Results for clinical outcome on the International Knee Documentation Committee (IKDC) subjective score, the EuroQoL 5-dimensions (EQ-5D) and the Tegner activity scale demonstrated no significant differences between the PRP group and HA group at 2 or 5 years. Within the first 2 years of treatment, rate of reintervention, including either repeat injection therapy or surgery, was significantly lower in the PRP group compared to the HA group. However, at 5 years, the rate of reintervention did not significantly differ between groups.