Knee osteoarthritis (KOA) is a pervasive and debilitating disease, affecting over 15 million people in the US alone. Symptoms include pain, stiffness, and ultimately loss of joint function. Medical therapies are the mainstay of treatment as surgical joint replacement is typically reserved for advanced disease. Only half of patients treated by medical management with disease not severe enough to warrant surgery experience adequate pain relief, resulting in an estimated population of 3.6 million Americans who are left suffering. Genicular artery embolization (GAE) is a novel, minimally invasive treatment that uses radiologic techniques to catheterize pathologically hyperemic genicular arteries using live X-ray guidance with subsequent occlusion of these vessels using injected microspheres. GAE is performed to inhibit or blunt synovial inflammation thought to be a primary phenotype of KOA. Multiple small sized cohort studies have shown to significantly reduce pain associated with KOA. This procedure has been performed in the University of Chicago Medical Center and showed its effectiveness and safety. In this study, the investigators plan to establish a prospective database of patients undergoing GAE for KOA in order to further characterize its effectiveness with a longer follow-up and larger sample size. The investigators also hope to establish Magnetic Resonance Imaging (MRI) as an objective imaging biomarker for positive remodeling of the knee that occurs after GAE due to decreased synovitis. If the results of this study are positive, the investigators plan to conduct a definitive sham-controlled study to justify the use of GAE in medically refractory KOA and help provide a treatment option to the millions of people with this disease.