Genicular artery embolization (GAE): a minimally invasive treatment for knee osteoarthritis pain. Indications, technique, and clinical outcomes.

Introduction

Knee osteoarthritis (gonarthrosis) is a leading cause of chronic pain and functional limitation in the adult population. Its prevalence increases progressively with age: over 20–25% of subjects over 50 show radiological signs of osteoarthritis, while approximately 10–15% develop clinically significant symptoms.

Chronic pain from knee osteoarthritis is multifactorial and not always directly related to the degree of cartilage degeneration. This explains why a significant proportion of patients continue to experience symptoms despite standard treatments such as physiotherapy, anti-inflammatory drugs, and intra-articular injections.

In recent years, a new pathophysiological paradigm has emerged: the role of synovitis and pathological neoangiogenesis as the primary drivers of pain. This is the basis for the development of genicular artery embolization (GAE), an interventional radiology procedure that aims to selectively reduce the pathological vascularization of the synovium.

Pathophysiological rationale

Traditionally, arthritis pain was attributed primarily to cartilage degeneration. However, cartilage is a non-innervated tissue and therefore not directly responsible for pain.

The most recent evidence indicates that:

• the synovial membrane is frequently the site of chronic inflammation

• pathological neoangiogenesis develops

• the new vessels are accompanied by nociceptive nerve fibers

  
  

This neurovascular complex contributes directly to the perception of pain.

Magnetic resonance and Doppler studies have shown:

• correlation between synovitis and pain intensity

• association between hypervascularization and symptoms

👉 GAE intervenes exactly on this mechanism, reducing the flow in the pathological vessels.

Mechanism of action

The effectiveness of the GAE is based on:

• Reduction of neoangiogenesis

• selective occlusion of pathological vessels

• Anti-inflammatory effect

• reduction of pro-inflammatory mediators

• Nociceptive modulation

• Reduction of associated nerve fibers

Directions

Main indication

Genicular artery embolization is indicated in patients with:

• symptomatic gonarthrosis

• persistent chronic pain (>3–6 months)

• failure of conservative therapy

Clinical criteria

Ideal candidates have:

• pain VAS ≥ 5/10

• significant functional limitation

• insufficient response to:

• FANS

• physiotherapy

• infiltrations

Ideal patient profile

• mild-moderate arthrosis (Kellgren-Lawrence II–III)

• evident inflammatory component

• localized pain (medial or lateral)

• Advanced directions

  
  

GAE also finds application in more complex scenarios:

• Patients not eligible for surgery

• Relevant comorbidities

• High anesthetic risk

• Young patients

• Need to delay prosthesis

• High functional demand

• Failure of hyaluronic acid, corticosteroid, and PRP injections

Contraindications

Absolute

• active joint infection

• uncontrollable allergy to the contrast medium

• severe renal failure

Relative

• coagulopathies

• significant peripheral arterial disease

Pre-procedural evaluation

• Clinic

• VAS scale

• pain pattern

Imaging

• load-bearing X-ray

• MRI (synovitis, bone edema)

• Doppler ultrasound

Laboratory

• kidney function

• coagulation

  
  

Procedural technique

The procedure is performed in an angiography room, under local anesthesia.

Relevant vascular anatomy

The knee has a rich and complex arterial network, arising mainly from the popliteal artery.

Major branches include:

• medial and lateral superior genicular artery

• medial and lateral inferior genicular artery

• middle genicular artery

These branches form a periarticular anastomotic circle, which ensures redundant perfusion.

1. Arterial access

• common femoral artery (most common)

• alternative: radial access

2. Selective catheterization

• use of 4–5 Fr catheters

• microcatheters for selectivity

Using fluoroscopic guidance, the arteries are navigated with vascular catheters, small plastic tubes a few mm in diameter, until they reach the genicular arteries.

3. Diagnostic angiography

• identification of synovial blush

• correlation with location of pain

  
  

4. Embolization

• calibrated particles (100–300 μm)

• progressive and controlled release

5. Final inspection

• blush reduction

• preservation of physiological flow

From an interventional point of view, it is essential to identify the branches responsible for the synovitis, avoid non-selective embolizations and preserve the perfusion of healthy tissues.

Average duration: 60–90 minutes

Post-procedural course

• same-day discharge

• resumption of daily activities: 24–48h

• sporting activity: progressive

Complications

Overall rate <5%

• post-procedural pain (10–20%)

• access hematoma

• skin ischemia (rare)

Clinical results

The available data shows:

Pain

• VAS reduction: 40–70%

• improvement within 1–3 months

Function

• improvement: 30–60%

Duration

• 6-month benefit: ~70%

• at 12 months: 60–70%

Response rate

• responders: 65–80%

• non-responders: 20–30%

Expected benefits

Based on the above, it can be seen that in 65 - 80% of treated patients a significant reduction in pain will be achieved, with an improvement in mobility and an increase in load tolerance which will allow them to return to normal daily activities and perform light sports.

It should be noted that improvement is not immediate but progressive; maximum benefit is achieved within 2–3 months, with some initial mild pain possible.

In non-responders, whose results are below expectations, the procedure does not preclude different types of treatments, infiltrative or otherwise.

Conclusions

Genicular artery embolization is a minimally invasive, safe, and effective procedure in selected patients. It directly targets the pathophysiological mechanism of arthritic pain, offering a valid therapeutic alternative in cases resistant to conservative treatments.