Knee osteoarthritis:

Osteoarthritis of the knee is an extremely common condition which affects millions of Australians and can negatively impact quality of life and the ability to stay active. Patients may obtain relief through lifestyle measures such as weight management, exercise and adjunctive therapies including thermal therapy, massage and mobilisation, physiotherapy as well as use of nonsteroidal anti-inflammatory drugs and joint injections.

Despite the above, there is a large population of patients who still suffer persistent pain daily but have few options available other than to continue daily analgesia use plus minus occasional intra-articular corticosteroid injections for flares and possibly other intraarticular injections such as hyaluronic acid and PRP. 

Patients may have to endure pain for many years before the knee has significant enough degenerative changes to warrant a knee replacement.

Orthopaedic surgeons generally like to delay knee replacement until there is advanced degenerative changes on the imaging studies and the patient is requesting surgery.

Until recently, there has been a dearth of options for the many patients in this scenario which may persist for decades however there have been recent advances and publications in embolisation therapy which offer a minimally invasive option which may be offered for these patients.

Osteoarthritis pain as an inflammatory problem:

Traditionally osteoarthritis has been thought of as a wear and tear physical degeneration condition however inflammatory mediators produced by thickening of the synovium (synovial hypertrophy) are a major pain generator in the osteoarthritic knee. Suppression of this inflammatory component may currently be achieved by NSAIDs and cortisone injections but the effect is temporary.

Embolisation is a minimally invasive technique designed to reduce blood flow to thickened synovium and in so doing induce reduction in synovial hypertrophy which reduces the local inflammatory environment in the knee.

Embolisation in the knee is known to be safe and effective at reducing synovial hypertrophy in patients with troubling haemarthrosis which occasionally occurs after knee replacement surgery and in haemophilia. The same technique (with modification) is now being applied to reduce synovial hypertrophy in the osteoarthritic knee, decreasing local inflammation and pain.

Genicular Artery Embolisation (GAE)

A few years back, at Royal Prince Alfred Hospital, we published the outcomes of embolisation for knee haemarthrosis in the Australian context and this is well established therapy for this uncommon condition after knee replacement and in patients with haemophilia.

Over the last 10 years, especially in Japan and the USA, genicular artery embolisation has been offered for knee osteoarthritis and the studies to date have shown a low risk profile for this day procedure and a substantial reduction in knee pain out to at least 24 months. I have personally spoken with key opinion leaders from around the world in interventional radiology and there is significant optimism about the future scope of this therapy.

The procedure:

GAE is performed as a day procedure under local anaesthetic +/- light conscious sedation. After the access site is numbed, a thin flexible catheter is introduced into the lower limb artery and the blood supply to the synovium is mapped with attention to identifying the abnormal increased vasculature seen in the symptomatic osteoarthritic knee. Generally this may predominated in either the medial or lateral compartment and often the treatment is focused to the more symptomatic compartment.

A very thin (less than 1 mm) flexible microcatheter is steered into the genicular artery which supplies the abnormal synovium and microscopic particles designed to reduce blood flow are trickled into the vessels to reduce blood flow (embolism) back down towards physiologic levels. Following introduction of the embolic agent, blood vessels are again mapped on completion and the catheter is removed. The patient can be discharged home that afternoon.

There is requirement for a couple of days off strenuous exercise and heavy lifting to minimise bruising risk and there may be a temporary flare of knee arthritis pain for a few days. Potential complications described in literature include bruising in the groin as well as a temporary skin rash but generally the risk profile is very low.

A new field of minimally invasive MSK treatment?

Momentum is building internationally for a new field of what is called MSK embolotherapy because the same technique described above in the knee has been shown to also have some benefit in other chronic inflammatory pathologies affecting tendons and joints.

Conditions where this has shown to be potentially beneficial include:

Frozen shoulder

Achilles tendinopathy,

Golfer’s and tennis elbow.

However data is still in the early days for applications outside of the knee joint. As president of the Interventional Radiology Society of Australasia I am in early discussions to establish a national registry to better capture track outcomes and data in this emerging area. 

Patient evaluation:

Patients are generally screened for suitability for the procedure based on their level of knee pain, and a questionnaire regarding the function PRE and post procedure is normally administered.

All patients will need an x-ray to exclude advanced degenerative changes which are much more appropriately treated with surgery and generally an MRI is helpful to exclude any acute knee injuries and assess the state of the degenerative changes in more detail.

I like to work collaboratively with orthopaedic surgeons where appropriate and will normally liaise or refer to discuss in cases where patients may have other pathology causing pain or more advanced changes that are more suitable for consideration for surgery.

There are also other contexts in which genicular artery embolisation may prove useful but are not yet well established. Areas of research include obvious potential in monoarticular inflammatory conditions as well as a potential role in patients who have persistent knee pain after total knee replacement.

Patients you may want to consider referring to discuss an embolisation procedure:

• Troubled daily by knee osteoarthritis pain.
• Pain localises to the medial or lateral knee.
• X-ray knee shows relatively intact knee joint with early degenerative changes
• X-ray does not show severe advanced changes “bone on bone” which may be best treated surgically.
• The patient may have already seen a surgeon and not currently be a candidate for surgery.