Interventional approach to chronic knee pain
The first step in clarification at the IISZ is often to find out which nerves are mediating the knee pain. Pain from the knee joint itself is often mediated via the so-called genicular nerves, while more superficial nerve branches, such as the saphenous nerve, play a role in Diagnosing nerve painneuropathic pain. Targeted and selective local anesthesia of these nerves can therefore be used to determine whether the pain is joint pain or neuropathic pain.
Diagnostic anesthesia of a knee joint nerve using ultrasound
Example of ultrasound guided diagnostic block of a genicular nerve. Red: femur, blue: local anesthetic, orange: nerve
Radiofrequency ablation of genicular nerves
If anesthesia of the genicular nerves provides satisfactory temporary pain relief, radiofrequency ablation of these nerves can be a useful treatment. A special cannula is placed as close as possible to the nerves under ultrasound or X-ray control and then heated using an electric current (radiofrequency). This interrupts the pain-conducting nerves, which leads to pain relief for a longer period of time.
Occasionally, cryoneurolysis can also be considered for neuropathic complaints of superficial nerve branches. In any case, before applying radiofrequency ablation or cryoneurolysis, it is important to find out in advance, with the help of test anesthesia (so-called diagnostic nerve blocks), via which nerve pathways the pain signals are being transmitted.
MRI image of a knee joint after radiofrequency ablation of the genicular nerves. It shows the extent of the radiofrequency lesions on both sides of the femur.
When is radiofrequency ablation of the knee joint nerves considered?
Radiofrequency ablation of the genicular nerves can be useful for patients with chronic pain due to knee osteoarthritis that cannot be treated in any other way: for example, if joint replacement surgery is not an option, or if joint pain persists despite an implanted knee prosthesis. As a rule, such therapy is only considered if conservative treatments alone do not lead to the desired success (e.g. pain medication, physiotherapy...).
What are the risks and side effects?
Radiofrequency ablation of the genicular nerves is a minimally invasive and relatively safe treatment. The most common side effects are temporary pain or slight inflammation at the puncture site. Serious complications such as nerve damage or infections are rare. In any case, however, it is important to bear in mind that the sclerosed nerves can grow back and the pain may return over time. On average, radiofrequency ablation of the knee joint nerves is effective for between 3-12 months. If it has been successful once, it can be repeated.
