Effectiveness and Safety of Embosphere Microspheres for Embolization of the Geniculate Artery for the Treatment of Pain With Known Moderate to Severe Knee Osteoarthritis

Inclusion Criteria: * Subject has signed informed consent * Subject is age 40-80 * Subject is able to have an MRI * Minimum of prior 12 weeks of failed response to conservative therapy for knee osteoarthritis, which may include one or more of: a) Oral or topical NSAIDS, opioid medications, intra-articular injection of glucocorticoids or hyaluronic acid, physical therapy. * Localized tenderness in anterior knee area * Kellgren-Lawrence grade 1, 2, or 3 as assessed by weight-bearing knee radiographs * Synovitis present as assessed by WORMS * VAS \>50 mm * WOMAC score \>30 Exclusion Criteria: * Rheumatoid arthritis * Local infection of the target knee(s) * Kellgren-Lawrence grade \>3 * Osteonecrosis evident by MRI * Prior knee arthroplasty * Allergy to iodinated contrast agents that cannot be managed by prophylaxis * Hypersensitivity to gelatin products * Any known condition that limits catheter-based intervention or is a contraindication to embolization * Active malignancy other than non-melanomatous skin cancer * Subject is pregnant, breastfeeding, or pre-menopausal and intending to become pregnant * Any other condition related to the subject's health and wellbeing deemed exclusionary in the opinion of the investigator