65 patients with knee osteoarthritis were randomized to receive intraarticular platelet-rich plasma (PRP) injections with exercise or exercise alone. The purpose of this randomized controlled trial was to determine the effect of PRP injections on pain, function, stiffness, and quality of life 6 months after treatment. The results displayed significantly greater improvements in WOMAC total and pain scores, and in the mental and physical domains of the SF-36 (quality of life), when compared to the control group at 6 months. Patients in the PRP group were found to consume significantly more acetaminophen during the study period.