Geniculate Embolization For Arthritis and Following Knee Replacement Surgery


Knee osteoarthritis and knee replacements (TKR) are very common. Whilst the vast majority of replacements are completely successful and result in a renewed quality of life, a small minority of patient’s following a TKR have ongoing symptoms and limitations. In addition many patients are keen to avoid a knee replacement for many reasons.

These ongoing symptoms  can include :

  1. Pain
  2. Limited range of movement
  3. Knee swelling
  4. Knee Effusions
  5. Joint Bleeds (Haemarthroses)

In some instances these symptoms may be related to the joint itself or other mechanical causes, however in many cases no clear cause can be found.

Vascular Causes of Knee Symptoms

There is increasing evidence and literature demonstrating an alternative cause of these symptoms may be associated with abnormal blood vessels forming in the tissues surrounding your knee joint. This can occur from osteoarthritis itself or as part of an abnormal healing process following knee surgery, new arteries can grow within and around the joint (known as the synovium). This is called “synovial neo-revascularization” (NSR).

Figure 1 : Angiographic evidence of NSR

These new blood vessels can result in :

  1. The synovium to become inflamed – causing pain
  2. The synovium to become thickened – causing limited range of movement
  3. The vessels can become leaky – causing effusions
  4. The vessels can bleed – causing joint bleeds

The treatment of NSR has been shown to improve outcomes in primary arthritic knees and following TKR.

Your Orthopaedic Surgeon would have excluded all alternate causes of pain following your knee replacement and when no other causes can be found, they may refer you to Mr Ponosh to investigate and treat alternate causes such as synovial neo-revascularization.

In many cases, your surgeon may refer you to Mr Ponosh to see if the treatment of NSR may postpone or delay the need for a replacement or improve your symptoms.

Mr Ponosh may organize a number of investigations to exclude other possible causes of pain and discomfort. These tests are bulk billed and conducted in Mr Ponosh’s rooms. They may including :

  1. Vein Ultrasound – to exclude poor functioning veins as a cause of pain and swelling
  2. Arterial Ultrasound – to exclude significant arterial disease that may be contributing to your symptoms and to exclude arterial disease that may make subsequent treatment difficult.

There is currently no definitive non-invasive test however available to diagnose NSR.

Treatment of Synovial Neo-vascularization


In some cases even though NSR is thought to be present, Mr Ponosh and your Orthopaedic Surgeon may decide a conservative approach is best suited to you. This decision is always made after a thorough discussion with you and the reasons explained. Of course, you can always choose a conservative treatment course which may include pain killers and physiotherapy.

Geniculate Embolization

Whilst the NSR and its treatment is gaining increasing acceptance and a strong body of international evidence supporting its effectiveness and safety in post TKR chronic symptoms, it is still considered a novel and relatively new procedure. It is not widely undertaken however, the elements of the procedure are routine and well accepted vascular interventions.

The treatment for NSR is through a procedure known as a Geniculate Artery Embolization (GAE).  The abnormal vessels that cause NSR arise from vessels which supply the knee and surrounding tissues known as geniculate arteries. Geniculate arteries are very small branch arteries that arise from the main arteries of your leg around your knee. GAE is a minimally invasive angiographic procedure to identify these abnormal vessels and embolize (block them). This stops inflammation, leaking and bleeding  associated with NSR and hopefully reduces or resolves your symptoms.

The procedure although novel, is extremely low risk and safe. Whilst no guarantee of outcome can be made, often patients referred for consideration of GAE have exhausted all other management options and have ongoing significant disability and lifestyle impairment effective their day to day lives. In this situation, given the low risk procedure and documented successful outcomes, GAE is a worthwhile and appropriate intervention.


Figure 2 : Resolution of NSR following Embolization

The procedure :

  1. Via a small (1-2 mm) incision in your groin, a small tube is placed in your arteries and the nature of the blood supply to your leg but especially surrounding your knee and joint is assessed through the injection of contrast dye under X-ray imaging.
    1. if the abnormal “blushing” of NSR is found, a tiny microcatheter is maneuvered into the supplying geniculate artery. These arteries are often less than 1-2mm in size. A liquid glue (Onyx) is injected via this microcatheter which travels into the even smaller NSR vessels and solidifies like permanent gel. This stops the abnormal vessel of NSR causing any further issues.
    2. If no abnormal vessels are found, no treatment is undertaken. Unfortunately there is no definitive non-invasive test to identify NSR.
  2. GAE is conducted as an overnight stay in hospital
  3. It is conducted in most cases under local anaesthetic and sedation with an anaesthetist present.

This is because :

  1. You are required to remain very still due to the delicate nature of the procedure and the tiny vessels that need to be accessed.
  2. The liquid embolic material known as Onyx when injected can cause pain and is best managed under anaesthesia.
  3. In almost all cases you are discharged home the next morning.
  4. Improvements or results are often immediate and improvements are reported over 6 weeks to 3 months.

Risks of GAE

  1. Outcome
    1. No guarantee of outcome can be made
      1. International trial’s and our local experience suggests most patients have mild-moderate improvement in symptoms. Some have complete resolution of symptoms
      2. Improvement of symptoms seems to be most significant if patients with haemarthroses (joint bleeds) and swelling but improvement is documented in all groups
      3. In most cases, patients have excluded all other treatment options thus this low risk procedure is of benefit
    2. Some patients have no improvement in symptoms
    3. Although worsening of symptoms is reported, the risk is very low and not seen in our local experience
  1. Risks of the Angiogram (see What is an Angiogram)


As the operation is performed on blood vessels a small amount of bleeding can sometimes occurs. This is often easily treated with some pressure but it is common to have some bruising to the area after the procedure. You may also develop a small lump which will resolve by itself. Serious bleeding is very uncommon but may require an additional procedure to correct.

False aneurysm

Very rarely a lump may occur which is in flow with the artery. This is because of some continued bleeding from the puncture site. This is called a pseudoaneurysm. This pseudoaneurysm may settle by themselves whilst other may require an additional procedure to fix them.


Pain and discomfort is usually minimal during the procedure and after. Occasionally you can get some bruising and discomfort to the groin in the following days but this is minor. If you are concerned or the pain is significant please seek advise.

Allergic reactions to the dye

Very rare

Damage to blood vessels

Usually these problems can be dealt with at the time of the procedure, but in rare instances, repair is necessary.

Equipment failure

It is theoretically possible for a catheter, wire or device to break and leave a fragment inside the body. This is extremely rare.

Failure of technique

Occasionally it is not possible to perform the procedure does not show the desired result. In very rare circumstances a failed procedure can actually make the blood flow worse. Catastrophic outcomes are very rare.

Kidney damage

The dye used is excreted via the kidneys, which in most patients is completely normal. However, especially in patients poor kidney function,  the dye can lead to deterioration in kidney function. Angiograms are used in patients with kidney disease often and safely but additional precautions are required such as admission the night before the procedure, additional fluids and modifying your medications. Mr Ponosh will discuss these with you. Patients on dialysis do not need additional precautions and angiograms are completely safe.

    3.  Standard risks of general anaesthetic and regional anaesthesia

Your risk for anaesthetic will be assessed initially by Mr Ponosh, but definitively by his Specialist Anaesthetists. They will discuss the low risk in detail.

  1. Post-procedural Pain

Pain post procedurally is normally minimal, managed with simple pain killers

    1. In approximately 5% cases, severe knee pain is reported that resolves over 7-14 days
      1. This is thought to be associated with the NSR “dying” off or resolving causing pain as it does.
      2. Pain killers and supportive measures are utilized
      3. No new chronic pain has been reported in our series
  1. Skin Changes
    1. The embolization to the abnormal NSR in rare circumstances interferes with the local blood supply to the skin in a small patch or two. This is seen in less than 5% of cases. This causes a dusky patch of skin that settles over a few weeks with simple dressings.
    2. Ulcers have not been reported
  1. Embolization Material
    1. Extremely low risk of the embolization material occluding vessels inadvertently.
    2. The Onyx embolizatiom material as it metabolizes does in some patients emit a odour often referred to as “onion” smell for 12 hours. It is not harmful but can be notable to visitors.