Femoral Nerve Block

What is a femoral nerve block?

A femoral nerve block is an injection of medication close to your femoral nerve to provide temporary pain relief (analgesia) or regional anesthesia. It can be a single injection or a continuous flow of medication.

Your femoral nerve is one of the largest nerves in your leg. It runs down the front of your thigh. Your femoral nerve has a motor function to help you move your hips, legs, ankles and feet. It also has a sensory function, helping you feel touch, pain and hot or cold temperatures. A femoral nerve block prevents pain signals from reaching your brain. But it can also temporarily “paralyze” your thigh and hip muscles for as long as the medication’s in effect.

Healthcare providers mainly use femoral nerve blocks to provide regional anesthesia for procedures in your thigh or knee regions.

Where is a femoral nerve block placed?

Healthcare providers inject a femoral nerve block in the middle of your upper thigh near your pelvis. Your femoral nerve comes from the lumbar plexus nerves. These are a collection of nerves that arise from the lumbar — or lower back — section of your spinal cord.

What muscles are affected by a femoral nerve block?

A femoral nerve block can temporarily affect your quad muscles (quadriceps femoris) — the muscles in front of your thigh — and hip flexor muscles (the psoas major and iliacus muscles).

What is a femoral nerve block used for?

Healthcare providers mainly use femoral nerve blocks for certain surgeries and to provide pain relief for acute (sudden and severe) injuries.

Regional anesthesia for surgeries

Surgeons use femoral nerve blocks to provide regional anesthesia for several procedures, including:

• Quadriceps muscle tear and tendon rupture repairs.
• Removal of a knee hematoma (pooling of blood under your skin) after total knee replacement (arthroplasty) surgery.
• Surgery on your patella (kneecap), such as to repair a patella fracture.
• Quadriceps muscle biopsy.
• Long saphenous vein stripping (removal or tying off of the saphenous vein).

Surgeons may use additional nerve blocks, such as a sciatic block or obturator block, for certain procedures. They may also use general anesthesia.

Surgeons also use femoral nerve blocks to manage your pain after major femur (thigh bone) and knee surgeries, such as a total knee replacement. This is usually a continuous nerve block.

Pain relief (analgesia)

Healthcare providers may use femoral nerve blocks to provide pain relief after you experience certain severe injuries, like:

• Femur fractures.
• Hip fractures.
• Femoral neck fractures (a specific type of intracapsular hip fracture).
• Patellar injuries.

Providers typically perform these blocks in an emergency department. They make it more comfortable for you when providers give physical exams and take X-rays. It also helps relieve pain if your provider needs to reset displaced broken bones (manipulation or closed reduction).

How should I prepare for a femoral nerve block?

If you’re getting a femoral nerve block for pain relief from an acute injury, you usually don’t have to do anything special to prepare.

If you’re getting a femoral nerve block for surgery, your provider will give you specific instructions. For example, you might need to fast (not eat or drink anything except water) before the surgery or stop taking certain medications.

What happens during a femoral nerve block?

The process for a femoral nerve block can vary slightly depending on if it’s for acute pain or surgery. It can also vary if it’s a single injection or a continuous flow with a catheter.

In general, you can expect the following when you receive a femoral nerve block:

• You’ll lie on your back on a procedure table.
• You may receive a mild sedative through an IV line in your arm to help you relax.
• A provider will measure certain vital signs throughout the procedure, like your blood oxygen level with a pulse oximeter, your heart health with an EKG and your blood pressure.
• The provider may use imaging guidance, such as ultrasound, to locate your femoral nerve and the exact spot where the injection needs to go. They may also use a nerve stimulator to locate your femoral nerve. This involves inserting a needle connected to a nerve stimulator machine into your nerve. The stimulator sends electrical signals. The provider knows they’ve reached the right nerve when your patella starts twitching.
• The provider will give you an injection of a local anesthetic to numb the area where you’ll receive the nerve block. You may still feel a pinch or some discomfort as the needle enters your skin.
• If it’s a single injection, they’ll inject the medication as close to the affected nerve(s) as possible. If it’s a continuous flow of medication, they’ll insert a catheter (a tiny flexible tube) near your nerve and secure it with medical tape on your skin.

What are the benefits of a femoral nerve block?

Femoral nerve blocks are often very effective for temporarily blocking pain.

For surgeries and acute injuries, a femoral nerve block can provide effective pain relief with a lesser need for opioid medications. As opioids have high addiction potential, this reduces the possible adverse effects of taking opioids. It may also allow you to leave the hospital earlier than if you were to take opioids only.

What are the risks or complications of a femoral nerve block?

Complications of femoral nerve blocks are rare but can include:

• Temporary or permanent nerve injury.
• Allergic reaction to the medication.
• Hematoma.
• Infection at the site of the injection.
• Local anesthetic systemic toxicity. This is a rare but potentially life-threatening reaction to local anesthesia. Your healthcare team will be prepared to treat it if it happens.

A femoral nerve block can increase your risk of falls as you recover from surgery in the hospital. This is because it can cause weakness in your quad muscles. Your healthcare team will discuss this with you and teach you how to prevent falls.

How long does a femoral nerve block last?

How long a femoral nerve block lasts can vary considerably.

The type, strength and dose of the anesthetic your healthcare provider uses affect the onset, duration and spread of the nerve block. Your provider will be able to give you a better idea of what to expect based on your unique situation.

In some cases, the nerve block might not work. Your healthcare team will provide other options for pain relief.

When should I call my healthcare provider?

Contact your healthcare provider immediately if you experience any new symptoms or complications from the femoral nerve block, such as an infection or nerve issues like burning pain, weakness or tingling.

A note from Cleveland Clinic

Femoral nerve blocks are a common and effective regional anesthesia method for various procedures affecting your thigh or knee. They can also provide temporary pain relief from certain bone fractures. If you’re feeling anxious about receiving a femoral nerve block, don’t hesitate to ask your healthcare provider about it and the procedure. They can answer any questions you may have.