Genicular Artery Embolisation (GAE) has emerged as a novel, minimally invasive treatment for symptomatic mild-to-moderate osteoarthritis of the knee and post-arthroplasty knee pain, and may provide immediate and long-lasting pain relief with improvement in patient function.

Osteoarthritis is a common disease and a major cause of morbidity. It has a rising incidence and prevalence, with data from the 2019 Global Burden of Disease Study1 showing the number of osteoarthritis cases in Australasia has increased by 116% in the last three decades, from an estimated 1.76 million cases in 1990 to 3.8 million cases in 2019, with the knee being the most commonly affected site. 

The most recent Australian National Health Survey (2017-18)2 estimates 3.6 million Australians are affected by arthritis, representing 15% of the total population, the majority of which are likely to be osteoarthritis, the most common form of arthritis. 

Treatment for knee osteoarthritis largely depends on disease severity. Treatment for mild and moderate osteoarthritis aims to reduce further joint injury through lifestyle and risk factor modification, involving physiotherapy and muscle strengthening exercise, weight loss, and pharmacologic therapy with paracetamol and topical or oral non-steroidal anti-inflammatory medications for analgesic effect. 

The role of glucocorticoid injection is controversial. Severe and end-stage osteoarthritis may be managed surgically, including with joint replacement. GAE may be an alternative treatment option for patients with mild-to-moderate osteoarthritis who have knee pain refractory to available conservative therapy but are not yet eligible or willing to undergo joint replacement, and for patients with severe osteoarthritis who are otherwise suboptimal surgical candidates. 

How GAE works

Osteoarthritis has long been considered a mechanical ‘wear-and-tear’ disease resulting from stress-related degeneration of articular cartilage. However, the role of inflammation and pathological angiogenesis in causing symptoms and disease progression in osteoarthritic joints has been established3-5. It is now understood that the chronic inflammatory synovitis that occurs with joint destruction drives regional angiogenesis and hypervascularity, which is accompanied by sensory nerve ingrowth along newly formed blood vessels. 

The resulting innervation of normally aneural periarticular tissues may be an important source of chronic pain and joint symptoms. The GAE technique is based on the theory that embolisation of abnormal synovial neo-vessels, which arise from the genicular arteries of the knee, is a potential target in the osteoarthritic joint to reduce the amount and effects of inflammation on the joint, which includes reducing ingrowth of sensory nerves into periarticular structures and release of pro-inflammatory mediators that exaggerate responses to pain stimuli3,6

Who does GAE work for?

Patients with mild-to-moderate osteoarthritis who have pain out of proportion to their radiological findings provide a challenge for general practitioners and orthopaedic surgeons who are faced with patients in considerable pain, often refractory to conservative measures, but without advanced enough changes to justify arthroplasty. GAE may help these patients manage their pain, but it does not appear to alter the natural history of joint degradation, with joint replacement still remaining the gold standard for those with severe osteoarthritis. 

The other subset of patients who seem to benefit from GAE are those who have undergone arthroplasty and still have a significant degree of postoperative pain despite routine measures such as physiotherapy.

How GAE is performed

GAE is a day-only, minimally invasive endovascular procedure that can be performed under local anaesthetic with or without sedation. The aim in GAE is to target the abnormal neo-vessel branches of the six genicular arteries that are responsible for the pathological hyperaemia, while maintaining the larger native genicular vessels that supply bone and serve as important collateral vessels in peripheral vascular disease.

Dark arrow - genicular artery selected at angiography
White arrow - the hypervascular blush in the synovium in Figure A
This has been “pruned” by embolisation in Figure B

Recent published data indicates that GAE is a safe and effective treatment in reducing knee pain from osteoarthritis3-5. Available studies include single-arm prospective trials, a retrospective case series, systematic reviews and a meta-analysis. Improvements in pain based on the Western Ontario and McMaster universities osteoarthritis index (WOMAC) or visual analog scale (VAS) scores have been shown in all studies, with early benefits of up to 50% pain reduction seen within one week and being sustained at 24 months across the cohort of studies5. Improvements in patient functional status have also been reported.

References

  1. Long, H., Liu, Q., Yin, H., Wang, K., Diao, N., Zhang, Y., Lin, J. and Guo, A. (2022), Prevalence Trends of Site-Specific Osteoarthritis From 1990 to 2019: Findings From the Global Burden of Disease Study 2019. Arthritis Rheumatol. https://doi.org/10.1002/art.42089
  2. Australian Bureau of Statistics, National Health Survey: First Results.
  3. Okuno Y, Korchi AM, Shinjo T, Kato S. Transcatheter arterial embolization as a treatment for medial knee pain in patients with mild to moderate osteoarthritis. Cardiovasc Intervent Radiol. 2015 Apr;38(2):336-43. doi: 10.1007/s00270-014-0944-8. 
  4. Padia SA, Genshaft S, Blumstein G, Plotnik A, Kim GHJ, Gilbert SJ, Lauko K, Stavrakis AI. Genicular Artery Embolization for the Treatment of Symptomatic Knee Osteoarthritis. JB JS Open Access. 2021 Oct 21;6(4):e21.00085. doi: 10.2106/JBJS.OA.21.00085. 
  5. Torkian P, Golzarian J, Chalian M, Clayton A, Rahimi-Dehgolan S, Tabibian E, Talaie R. Osteoarthritis-Related Knee Pain Treated With Genicular Artery Embolization: A Systematic Review and Meta-analysis. Orthop J Sports Med. 2021 Jul 14;9(7):23259671211021356. doi: 10.1177/23259671211021356.