Evaluating Changes in Synovial Fluid Before and After GAE for Knee Osteoarthritis

Inclusion Criteria: * Age ≥ 18 years * Planned to undergo genicular artery embolization to treat knee osteoarthritis. * Osteoarthritis on knee radiograph (Kellgren-Lawrence score 1-3) within the last 6 months * Persistent moderate to severe knee pain (visual analog scale \[VAS\] \>3) for at least 6 months * Pain refractory or intolerant to conservative therapies (e.g. analgesia, exercise, weight-loss, joint injections, physical therapy) * BMI \< 35 kg / m2 * Stated willingness to comply with study procedures and availability for the duration of the study Exclusion Criteria: * Coagulation disturbances not normalized by medical treatment (INR \>1.8 and platelets \<50 x 10\^9/L) * Receiving medications for anticoagulation which cannot safely be held for the procedure (e.g ASA for 5 days, Lovenox for 24 hours, Eliquis for 4-6 days depending on creatinine clearance * Allergy to iodinated contrast agents not responsive to steroid premedication regimen * Active knee joint infection * Acute knee injury with surgical indication (MRI evidence of acute fracture or ligamentous injury of the knee) * Prior total or partial knee replacement in the subject knee * Intra-articular steroid injection within 2 months * Untreated lower extremity vascular arterial disease * Untreated venous insufficiency * Presence of medical condition with life expectancy less than 6 months * Patients who have undergone previous lower extremity embolization * Patients with renal insufficiency based on an estimated GFR\<45 ml/min who are not already on hemodialysis * Patients who are pregnant or intend to become pregnant within 6 months of the procedure * American Society of Anesthesiologists classification \> 3 * Less than 3 mm of synovial fluid in the lateral suprapatellar recess on MRI or US