What is popliteal nerve block?

Black-and-white radiological image with measuring lines and color code showing the popliteal nerve.
This image is similar to what a doctor might see on an ultrasound when locating the popliteal nerve to administer anesthetic for a popliteal nerve block.

Popliteal nerve block is a type of anesthetic procedure that blocks the sciatic nerve and blocks pain in the lower leg, including 

  • the calf, 
  • shin, 
  • fibula, 
  • ankle, and 
  • foot. 

The sciatic nerve starts in the lower back (lumbar spine) and travels down the leg, deep inside the thigh. Behind the knee, the sciatic nerve divides into the peroneal and tibial nerves and moves closer to the skin’s surface. It is in this area where the nerves are closer to the skin’s surface that anesthetic can be placed to numb the nerve.

What is popliteal nerve block used for?

Popliteal nerve block is used 

  • to control pain before or after surgery in the area below the kneecap (patella) and
  • as a regional nerve block to numb the leg in cases of severe trauma or large lacerations to the area that need to be repaired. 

How do doctors perform a popliteal nerve block?

Popliteal nerve block is performed by injecting local anesthetic (usually lidocaine or bupivacaine) with a small needle behind the knee. 

Sometimes an ultrasound machine is used to locate the nerve that runs behind the leg. 

Injecting an anesthetic in the area of the nerve behind the knee will numb all the structures served by that nerve, which include the calf, shin, fibula, ankle, and foot. 

The following are the usual steps for performing a popliteal nerve block:

  • The patient is positioned laying prone on the stomach. 
  • An ultrasound machine is sometimes used to find the location of the nerve at the knee. 
  • The area to be anesthetized behind the knee is draped with sterile drapes and prepped with a cleaning solution, usually betadine or chlorhexidine. 
  • The anesthetic (usually lidocaine or bupivacaine) is slowly injected into the area around the nerve, being careful not to inject directly into the nerve or the vascular structures nearby. 
  • After a few minutes, the patients will notice numbness in the area of the lower leg, ankle, or foot. 
  • The area where the anesthetic was injected is cleaned again, and a sterile bandage is placed over the area. 
  • The anesthesia (numbness) from the nerve block can last from 30 minutes to 36 hours, depending on the anesthetic used.

How long does popliteal nerve block last?

Popliteal nerve block performed with a short-acting local anesthetic can last between 30 minutes to one hour. When performed with long-acting local anesthetics, the nerve block can provide between 12 to 36 hours of pain relief after foot surgery.

What are the risks and complications of a popliteal nerve block?

Complications of a popliteal nerve block procedure include:

  • Infection: Any procedure that involves injecting medications into the skin has the potential to cause infection. This can occur if the injection site is not properly cleaned prior to the procedure. 
  • Nerve injury: If the anesthetic medication is injected into the nerve itself, it may result in temporary or permanent damage to the nerve. The patient may have numbness, tingling, or pain, at the site of the injection if this occurs. 
  • Allergic reaction: Most anesthetic blocks are safe and rarely cause allergic reactions. When allergic reactions occur, they can range from delayed hypersensitivity (mild itching and swelling) to full anaphylactic shock. If you have a known allergy to injectable anesthetic medications such as lidocaine or bupivacaine, discuss this with your doctor prior to receiving a popliteal nerve block. 
  • Bleeding: Because a popliteal nerve block is performed with injectable medication, bleeding under the skin (bruise or hematoma) may occur.

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Medically Reviewed on 4/14/2020
References
Medscape Reference

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