Genicular Anatomy
Genicular anatomy refers to the network of nerves and arteries around the knee joint, which are helpful for its function, sensory perception, and blood supply. The genicular nerves provide sensory innervation to the knee. They can potentially be targeted by interventional pain physicians with temporary nerve blocks or radiofrequency ablation (RFA) for longer relief.
What is a Genicular Nerve Block?
A genicular nerve block is an injection of a local anesthetic (+/- corticosteroid) administered near the genicular nerves to temporarily block the pain signal carried from the knee to the brain. It assists your doctor in diagnosing a potential cause of your chronic knee pain.
If a genicular block is successful in confirming that the pain is originating from the genicular nerves, radiofrequency rhizotomy/ablation (RFA) is suggested to provide longer pain relief.
What is Genicular Radiofrequency Ablation?
Genicular nerve radiofrequency ablation is a non-surgical procedure that uses radiofrequency energy to provide long-term pain relief for chronic knee pain. A doctor uses a special needle to deliver controlled heat to the genicular nerves that supply knee sensation. This heat “knocks out” or denatures the nerves, reducing or eliminating the pain signals to the brain.
Indications and Contraindications of Genicular Nerve Block
Genicular nerve blocks are usually indicated for chronic knee pain that originates from degenerative arthritic changes or to manage pain after knee surgery.
The procedure cannot be performed if you have an active infection or potentially have not been cleared by your orthopedic knee surgeon if post-surgery pain is why you are receiving this procedure. Also, inform your doctor if you are allergic to medications used in the procedure. Be sure to discuss these situations with your doctor before the procedure.
Preparing for a Genicular Nerve Block/Radiofrequency Ablation
You are advised to avoid driving after receiving this procedure, as well as any moderate-strenuous activity for several days. A driver will be needed to take you home regardless of receiving sedation or not. It is also required to not eat or drink for at least 4-6 hours prior to the procedure. You may take your approved medications with a sip of water.
*It is important to keep in mind with Radiofrequency Ablation procedures that pain relief can take several weeks to occur. The genicular nerves must denature and this can take a few weeks for maximum benefit.
Genicular Nerve Block and RFA Procedure
- A genicular nerve block and RFA procedure is performed under fluoroscopy (X-ray) guidance to ensure the accurate placement of the needle and to avoid nerve/other structural injuries.
- You will be made to lie on your back on an X-ray table, usually with pillow support under the knee to be treated. The area of the skin to be injected is cleaned properly and a local anesthetic administered to numb the skin. A stinging or burning sensation may be felt for a few seconds. A small needle is then directed towards the superior medial and lateral + inferior medial sites of the knee (3 sites per knee in total), under X-ray (fluoroscopy) guidance. AP and lateral X-ray will be used to confirm proper placement anatomically. A small mixture of the numbing agent +/- steroid medication is then slowly injected over the targeted nerves.
- For Radiofrequency Ablation (RFA), this procedure will usually take longer (10-20 minutes per knee). Electrical energy is applied to the needles after they are in position at the genicular nerves and heat is generated on the nerves to provide the treatment.
- This is an outpatient procedure and you can go home the same day. A driver will need to pick you up. You may eat/drink after the procedure and resume normal medications.
What to Expect after a Genicular Nerve Block
After the Genicular nerve block, your pain may
- Be relieved for a few hours
- Be relieved for a few days
- Not reduce at all
If the pain is relieved after the genicular branch block, it indicates that the origin of the pain is the genicular branch nerves supplying the knee.
Based on the amount of pain relief observed during the first 6-24 hours after the injection, you may be considered suitable for the radiofrequency ablation (rhizotomy) procedure to relieve the pain for a longer period.
In radiofrequency ablation, an electrical current is passed through a needle at the selected genicular branch nerve causing heat to interrupt the pain signals of those nerves. This is a procedure that hopefully can provide longer lasting relief for chronic degenerative knee pain or post-surgical knee pain.
Post-procedural Care following a Genicular Nerve Block/RFA
- You should arrange for someone to drive you home after the procedure.
- You may continue your routine prescribed medications after a gap of 4-6 hours following the procedure to avoid incorrect assessment of diagnostic results related to pain relief.
- You may experience localized pain at the injection site in the first 2-3 days, for which ice packs can be applied to ease the discomfort.
- You can return to your regular activities, a day after the procedure for the nerve blocks and usually the RFA as well. Increased soreness and discomfort is expected after the RFA compared to the blocks. It is recommended to anticipate lighter activities after the RFA for 2-3 days. There are no major restrictions to activity but mild-moderate discomfort may limit them.
* Important to know – your physician may ask you to go home after the procedure and do light activity (such as walking, bending, standing) to prove that you feel diagnostic pain relief the day of the genicular nerve block procedure. This is to better assess if you truly have a positive genicular nerve block and relief of pain from the knee.
- In cases where improvement in the pain is seen, you are advised to perform moderate activities, with regular exercises.
Risks and Complications a Genicular Nerve Block
Although a genicular branch block/RFA procedure is a safe procedure, the possible risks and complications associated with the procedure may include:
- Allergic reaction
- Bleeding and bruising at the site of injection
- Infection at the site of injection
- Discomfort at the site of injection
- Temporary numbness
- Increased pain
- More serious but very rare complications are vascular injury, nerve injury leading to foot drop, as well as skin burns after RFA.
