What Is a Peripheral Nerve Block?

A peripheral nerve block is a procedure done by an anesthesiologist to provide postoperative pain relief for people having knee replacement surgery. The anesthesiologist (a doctor specializing in pain management) places numbing medicine (local anesthetic) near the nerves to your knee. The block lasts about 24 hours after surgery and can help you feel better right after surgery.  

Most patients say that the pain they experience after a knee replacement is most intense in the first 24 hours after surgery. A peripheral nerve block, in addition to oral or intravenous pain medications, provides patients with the best pain relief possible during this early recovery phase. It is important to realize that even with the nerve block, you will not be completely pain-free. However, your pain will be much more manageable with the nerve block.

How Does a Peripheral Nerve Block Work?

Your peripheral nerves send pain signals to the brain. The peripheral nerve block prevents pain signals from the knee from reaching the brain. The nerve block causes numbness in the knee but should not cause muscle weakness. Pain relief from a peripheral nerve block usually lasts about 24 hours. By then, most patients find they require much less pain medication to manage their symptoms. 

Nerve Block Pros & Cons

Our orthopedic surgeons recommend peripheral nerve blocks for people having knee replacement surgery. Patients who get peripheral nerve blocks will:  

  • avoid the intense pain that can occur in the 24 hours after surgery;
  • be able to rely less on opioid medications, which can dangerously affect their breathing, make them dizzy, nauseous, constipated, and itchy;
  • allow them to more fully participate in rehabilitation therapy because their pain is well-managed; and 
  • be more active after surgery, which lowers their risk of surgical complications such as blood clots and stiffness.

Nerve Block Side Effects

You will experience numbness in your leg until the peripheral nerve block wears off. The nerve block does not affect your strength. If you experience thigh weakness, please contact someone from the care team. Be sure to follow the instructions regarding walking and standing.

Peripheral Nerve Block Complications 

Peripheral nerve blocks are considered to be a safe option for almost everyone. Complications from peripheral nerve blocks are extremely rare. They include:

    • risk of infection at the injection site,
    • bleeding at the injection site, 
    • seizures or abnormal heart rhythms, and 
    • prolonged numbness in your thigh.

Your anesthesiologist will talk to you about these concerns on the day of your surgery, especially if your health history suggests you may be at higher risk for complications. 

Peripheral Nerve Block Procedure

One of our anesthesiologists with advanced training in nerve blocks will administer the peripheral nerve block. This takes place in the recovery room after surgery. The anesthesiologist will:

  • use ultrasound guidance to pinpoint the location of the nerve in your knee, and
  • inject the nerve-numbing medication near the nerve.

The process takes about 10 minutes. You may notice pain relief within 15 to 20 minutes. The full effect may take up to 30 minutes or longer.

Do Peripheral Nerve Blocks Hurt?

Receiving a peripheral nerve block is not painful for most patients. You may feel a pinch when the doctor inserts the needle into your skin. 

How Long Does a Nerve Block Last after Surgery?

Pain relief from a peripheral nerve block lasts between 18 and 36 hours—on average, about 24 hours.

Signs a Nerve Block Is Wearing Off

As the nerve block medication wears off, most patients experience increasing achiness in their knee. If your knee still feels numb after 48 hours, call our surgical team to let them know.

Pain Relief after the Nerve Block

Peripheral nerve blocks are part of a balanced approach to pain relief that involves combining different types of medications to achieve the best pain relief for patients with the fewest side effects. These medications work together, targeting different pain pathways.

Peripheral nerve blocks are just part of the pain relief picture for people who have had knee replacement surgery. Your doctor may also prescribe:

  • acetaminophen (Tylenol),
  • non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil, Motrin, etc.), or naproxen sodium (Aleve),
  • muscle relaxers,
  • medicines that target nerve pain, and
  • opioid medication.

Our care team will provide detailed instructions to help you manage pain symptoms after surgery and help you know what to expect during the knee replacement recovery process.