The purpose of this research study is to evaluate the effectiveness and safety of a permanent embolic (Embosphere Microspheres) for embolization of the geniculate artery for the treatment of 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