Nerve blocks are used in patients undergoing knee ligament surgery under general or spinal anesthesia, in combination with a genicular nerve block, to relieve pain after the procedure.
What is a genicular nerve block?
The genicular nerves run around the femur and tibia and transmit pain sensations from the knee joint. By injecting a local anesthetic around the knee, these nerves are “blocked”: the knee becomes numb and feels heavy, and the patient does not feel pain, although they may still feel movement or pressure when the doctors move the leg during surgery.
Injection of the anesthetic around the knee
The nerve block provides pain relief for up to 24 hours after surgery; in some areas, sensation may remain reduced for up to 48 hours. During general anesthesia, a lower dose of anesthetic is therefore required, which can result in faster recovery from anesthesia and less nausea after the procedure. Not all anesthesiologists perform this procedure, as it is a specialist technique.
Benefits of nerve blocks
The procedure provides better pain relief after surgery, reduces the need for strong painkillers, allows lower doses of anesthetic to be used during general anesthesia, and promotes faster recovery, improved mobility and earlier discharge from hospital.
How is the nerve block performed?
The injection is administered in a room near the operating theatre, with sedation if necessary. The skin is first numbed with a local anesthetic, after which the anesthesiologist uses an ultrasound device to locate the nerves.
The knee initially feels warm and tingly, then gradually becomes heavy and numb. The effect develops within 20–40 minutes. The patient is taken to the operating theatre only once the anesthesiologist is satisfied that the nerve block is working. If the block is not completely effective, the patient receives additional anesthetic or other pain medication.
After the procedure and at home
While the nerve block is active, the knee is “numb” and may be more difficult to move, so the patient may need assistance with everyday activities.
As the effect wears off, tingling in the knee is completely normal. Numbness can last for up to 48 hours. During this period, the patient should avoid operating machinery or household appliances, for example, as the risk of injury is higher when sensation in the knee is reduced.
Risks
Serious complications are rare. A common but harmless effect is reduced awareness of the position of the leg, resulting in a “numb” or “deaf” feeling in the knee, which resolves as the nerve block wears off.
Bleeding at the injection site is relatively common but can be controlled by applying pressure. Nerve injury occurs in approximately 1 in 700 to 1 in 5,000 nerve blocks. Mild, temporary tingling or numbness occurs in approximately 1 in 10 patients; it resolves within six weeks in 95% of patients and within one year in 99% of patients.
The risk of accidentally injecting the anesthetic directly into a blood vessel, stroke or another serious complication is very low.
If you experience severe pain that cannot be controlled with painkillers after the nerve block, contact emergency medical services immediately.