Several clinical trials on genicular artery embolization (GAE) show significant clinical benefit for the majority of patients. However, a proportion of patients do not benefit from GAE, and responses vary across individual patients. Changes in metabolic activity on non-invasive imaging may correlate with improvement in symptoms of knee osteoarthritis. This study will assess changes in metabolic uptake on a hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) system in subjects undergoing GAE.