Genicular Nerve Block
A genicular nerve block is the injection of a local anaesthetic to block the nerves that transmits pain from the knee.
What is the purpose of a facet nerve block?
A genicular nerve block is a diagnostic procedure to determine if the pathologic changes (i.e. arthritis, meniscal tears, etc.) and inflammation within the knee joint is the source of your knee pain. It also confirms that the knee pain will respond well to the actual treatment procedure. If a genicular nerve block works, it will give you relief for up to 24 hours, this may vary from patient to patient. After that, the pain is expected to return to normal. If a reduction in 50% or more in pain is experienced, then we would schedule a treatment called radiofrequency (RF) ablation. In this procedure, the same nerves are cauterized, which typically leads to pain relief for 12-18 months. If this process works well for one knee, it can be performed on the other knee if needed.
How is the procedure performed?
You will be placed on the procedure table. The injection site is sterilized with either iodine or chlorhexidine. The site to be injected is numbed with a local anaesthetic, and a needle is directed to the target area. X-ray guidance is used to ensure proper placement and positioning of the needle. When the needle is properly positioned near the genicular nerve, local anaesthetic is injected to numb that nerve. This will be repeated at multiple sites around the knee to block all genicular nerves.
Will the procedure be painful?
The injection can be painful and we therefore patients receive light IV sedation. IV sedation, combined with local anaesthetic, can make the injection nearly pain free. It allows you to remain very still during the procedure, which can also make the injection easier, faster, and more successful. With IV sedation, you must have a driver to get you home safely afterwards. In addition, you cannot have anything to eat or drink within 6 hours of your appointment (clear liquids are allowed until 2 hours before the procedure). If you take medications for diabetes, these medications may need to be adjusted the morning of the procedure. Your primary care physician can help you with this adjustment.
What are the discharge instructions?
If you received IV sedation do not drive or operate machinery for at least 24 hours after the procedure. You may return to work the next day following your procedure. You may resume your normal diet immediately. Do not engage in any strenuous activity for 24 hours. You should, however, engage in moderate activity that typically causes your usual pain. If the block works, those activities should not be painful for up to hours after the injection. Call the office if you have any of the following: severe pain afterwards (different than your usual symptoms), redness/swelling/discharge at the injection site(s), fevers/chills, difficulty with bowel or bladder functions.
What are the risks and side effects?
The complication rate for this procedure is very low. Whenever a needle enters the skin, bleeding or infection can occur. Some other serious but extremely rare risks include paralysis and death.
You may have an allergic reaction to any of the medications used. If you have a known allergy to any medications, especially local anaesthetics, notify our staff before the procedure takes place.
You may experience any of the following side effects up to 4 hours after the procedure:
Leg muscle weakness or numbness may occur due to the local anaesthetic affecting the nerves that control your legs (this is a temporary affect and it is not paralysis). If you have any leg weakness or numbness, walk only with assistance in order to prevent falls and injury. Your leg strength will return slowly and completely.
Dizziness may occur due to a decrease in your blood pressure. If this occurs, remain in a seated or lying position. Gradually sit up, and then stand after at least 10 minutes of sitting.
Mild headaches may occur. Drink fluids and take pain medications if needed.
Mild discomfort at the injection site can occur. This typically lasts for a few hours but can persist for a couple days. If this occurs, take anti-inflammatories or pain medications; apply ice to the area the day of the procedure. If it persists, apply moist heat in the day(s) following.
The side effects listed above can be normal. They are not dangerous and will resolve on their own. If, however, you experience any of the following, a complication may have occurred and you should either contact your doctor. If he is not readily available, then you should proceed to the closest urgent care centre for evaluation.