Osteoarthritis (OA) is a major cause of chronic knee pain and disability with a reported prevalence of 25-30% of the population over 60 years of age. While traditionally thought of as a purely degenerative disease related to “wear and tear”, the pathophysiology of OA involves a complex interplay of mechanical, biological, and molecular factors leading to inflammation, pain, and structural degeneration.
Current treatments focus on symptom management (pharmacotherapy, physical therapy, surgical interventions). Geniculate artery embolisation (GAE) has emerged as a novel, minimally invasive endovascular procedure aimed at reducing articular inflammatory symptoms associated with OA.
Evidence is increasing that GAE can significantly reduce symptoms, postponing or delaying the need for total knee replacement (TKR). There is also an increasing role evident for GAE in suboptimal functional outcomes following a TKR where a similar inflammatory paradigm is thought to exist. This occurs on the background of a longstanding role of GAE in post TKR haemarthrosis.
Inflammatory mediator cascades induced by OA drive inflammatory pathways including abnormal articular and synovial neo-revascularisation (NSR). This angiogenesis has been linked to inflammatory changes to the articular surfaces and synovium, osteophytes, cartilage degeneration, and neuro-sensitisation.
Apart from driving ongoing OA degeneration, the synovial and articular angiogenesis and associated inflammation is thought to be a functional source of pain, swelling, haemarthroses and stiffness. GAE is thought to mitigate this abnormal angiogenesis, slowing the inflammatory OA drive, thus slowing the progression of degenerative OA changes and reducing symptoms.
GAE is not an isolated treatment option and needs to be considered as part of a tailored comprehensive approach, in close liaison and coordination with orthopaedic surgeons and other musculoskeletal physicians. It appears to have a greater role in mild to moderate OA compared to severe/end-stage as an adjunct management option between conservative management (e.g. physiotherapy, articular injections, pain management) and surgical intervention. This is of benefit in patients wishing to delay a TKR or patients deemed young or of “high risk” for TKR.
Over 60,000 knee replacements are conducted in Australia annually, with variable reports of suboptimal functional outcomes of 5-18%. While the cause of suboptimal TKR is complex, including mechanical, prosthetic or infective issues, a similar inflammatory paradigm of synovial inflammatory revascularisation and angiogenesis has been theorised.
GAE has developed an increasing role in treating pain, stiffness, haemarthrosis and swelling in patients with no clear mechanical cause who otherwise are looking at a revision TKR or conservative management.
GAE is a low-risk, minimally invasive, percutaneous endovascular procedure conducted under local anaesthetic and sedation. Under angiographic guidance, the geniculate arteries (vessels perfusing the knee arising from the femoral artery) are assessed for typical hypervascular inflammatory synovial blush consistent with inflammatory NSR.
While in some cases inflammatory synovitis can be seen on pre-procedure MRI/MRA or SPECT imaging in native knees, it is not always consistent with NSR and is of limited diagnostic benefit.
These modalities have limited merit in the setting of an existing TKR. If NSR is identified on the global or selective geniculate angiogram, the NSR is accessed via microcatheterisation via the feeding geniculate artery and embolised using microspheres or liquid embolic agents such as Medtronic Onyx. Coil embolisation is ineffective.
This aim is to treat NSR directly while minimising embolisation of geniculate vessels themselves. Multiple geniculate arteries are often needed to be catheterised as the NSR is often multifocal and multisourced. Procedure times are approximately 45-60 minutes as a day case or overnight stay with an average return to work within 4-7 days. Maximum benefit is seen after three months.
Technical success has been documented as 99.7%. Complications include groin access complications, non-target embolisation resulting in transient skin ischaemia (5-10% cases), which in almost all cases is self-limiting, temporary worsening of patient’s knee pain (10% cases) over 2-3 weeks and extremely rare complications such as osteonecrosis and distal embolisation.
The outcome of GAE in native knees in trials and meta-analysis (over 174 papers some with sham arms) showed robust results. Studies demonstrated statistically significant outcome measures and clinically important benefits at all follow-up intervals to 24 months. At two years, only 8.3% of cases required re-intervention with GAE, and 5.2 % underwent a TKR.
In post knee replacement GAE, local data suggests 82% of patients had statistically significant improvement at three months with the significant benefit maintained in 68% patients at 12 months. Post-24 month outcomes are pending.
Geniculate artery embolisation is a novel, minimally invasive procedure that may reduce pain and improve function in knee osteoarthritis. Targeting pathological neovascularisation associated with the disease, GAE addresses a key aspect of OA pathophysiology.
Early clinical outcomes are promising, suggesting that GAE may become an important tool in the multidisciplinary management of OA in close coordination with orthopaedic surgeons. With growing evidence, GAE could significantly impact OA treatment, providing relief for patients, reducing reliance on more invasive surgical procedures and long-term medication use.
Key messages
- Aside from degeneration, OA has an inflammatory component
- Geniculate artery embolisation may be an intermediate option between conservative and surgical management
- While still regarded as novel, evidence is mounting to support a role for GAE.
Author competing interests – the authors were involved in collecting “local data” for the post TKR trial