Multimodality imaging considerations for genicular artery embolization in knee osteoarthritis

Genicular artery embolization (GAE) describes a minimally invasive, catheter-directed therapy that targets abnormal hypervascular synovium and periarticular neovessels in patients with symptomatic knee osteoarthritis (OA), particularly those with inflammation-predominant disease who are poor surgical candidates or wish to defer arthroplasty. As clinical adoption expands, pre-, intra-, and post-procedure imaging has become increasingly relevant to both diagnostic and interventional radiologists. In practical terms, inflammation-predominant disease refers to knees with prominent synovitis-related magnetic resonance imaging (MRI) findings despite less advanced irreversible structural destruction, whereas structure-predominant disease is characterized by extensive cartilage loss, large bone marrow lesions, meniscal maceration, and advanced radiographic degeneration. Although no prospectively validated imaging cutoff exists for routine GAE candidate selection, current studies suggest that moderate-to-large effusion-synovitis (the combined appearance of joint fluid and synovial thickening on non-contrast MRI) (grade 2-3), greater overall MRI lesion burden (≥ 4 abnormalities), and extensive full-thickness cartilage loss may help distinguish these phenotypes. Synovial enhancement and effusion-synovitis on MRI are the findings most consistently expected to improve, whereas structural hallmarks of OA often persist and may be misinterpreted as treatment failure. Early marrow or subchondral signal alterations have also been reported after embolization and require cautious follow-up interpretation. This review summarizes contemporary evidence on pre-, intra-, and post-procedure imaging, semiquantitative MRI scoring systems, and common post-GAE interpretive pitfalls.