Chronic knee pain is a very limiting condition as it can interfere with day to day function and ambulation. Knee pain does not always respond to steroid or gel based injections. Even worse, it can somtimes persist despite having knee surgery. Genicular nerves are the sensory nerve endings which are responsible for the transmission of knee related to pain and can be targeted to treat knee pain.
What is a Genicular Nerve Block?
This is simply an injection of local anesthetic at three to sometimes four genicular nerves. It is done with X ray or ultrasound guidance.
The knee block procedure is primarily used as a diagnostic modality to determine if blocking these nerve endings provide significant pain relief. The nerve block’s effects last from eight hours to 24 hours and sometimes longer. If the first block works, the diagnostic test is performed a second time before the next step is taken.
Generally, if pain is reduced by at least 50 percent both times, then we follow it with radiofrequency ablation of these genicular nerves to provide more sustained pain relief.
Who can benefit from this procedure:
The people who are most likely to be candidates for the nerve block in the knee are those who:
- had a total or partial knee replacement, and the pain continued after the surgery,
- want knee surgery as a last resort option,
- have health issues that make knee replacement surgery too risky,
- have chronic knee pain due to degenerative joint disease (osteoarthritis)
- have a knee injury marked by chronic painful inflammation
- need pain relief before or after knee surgery
What to Expect During a Typical Procedure
During the procedure, the patient lies on a procedure table. The physician sterilizes the injection sites and numbs them with an anesthetic. Using a fluoroscope a needle is placed at the correct position near a genicular nerve. While inserted, a local anesthetic is administered to numb (block) the nerve to stop pain signaling.
In some cases, sedation may be used if needed. After the procedure, it is important to resume normal moderate activities that previously caused knee pain. This helps to determine whether the genicular nerve block for knee pain is effective.
Radiofrequency Ablation of Genicular Nerves
Long-term pain relief can be expected from radiofrequency ablation. Patients who have responded well to the diagnostic nerve block undergo the ablation procedure, usually done with local anesthetic on an outpatient basis. Once again, fluoroscopic or ultrasound guidance is used.
A thin cannula is guided as close as possible to the appropriate nerves, one at a time. Once in place, radiofrequency lesioning (ablation) involves inserting an electrode into the cannula so that an electrical current produced by a radio wave can heat up the tip of the needle. The hot tip of the needle then cauterizes the nerve transmitting pain signals, so it cannot transmit pain signals to the brain. The process is repeated for each nerve.
The pain relief from the genicular nerve ablation procedure can last from six months to one year, or even longer. It is a low risk procedure that is done on an outpatient basis.