40 patients with knee osteoarthritis were randomized to receive intra-articular triamcinolone injection followed by a 5ml intra-articular injection of autologous conditioned serum (ACS) (n=20) or a saline placebo (n=20). Outcomes of interest included pain on a Numeric Rating Scale (NRS), Knee Injury and Osteoarthritis Scale (KOOS), and the incidence of serious adverse events. Average, maximum, and at-rest knee pain on an NRS was significantly lower in the ACS group compared to the placebo group at 24 weeks. Similarly, pain at rest was also significantly lower in the ACS group. KOOS pain, symptoms, activities of daily life, sports, and quality of life were also significantly better in the ACS group after 24 weeks. KOOS sports was significantly better at 3 weeks in the ACS group. Overall, the ACS group demonstrated significant reductions in knee pain and notable improvements in overall function and quality of life compared to the placebo group suggesting a safe and effective intervention for knee osteoarthritis.