The Anatomy of the Femoral Nerve

The femoral nerve is the major nerve in your thigh. It's one of the largest leg nerves and runs from your pelvis down the front of your leg. The nerve signals carried by the femoral nerve are a critical part of the ability to stand, walk, and maintain balance.

Anatomy

Nerves are complex structures that branch out like a tree. Their many "limbs," called dendrites, connect from single cells to networks throughout your body, including skin, muscles, and connective tissues. From skin, they detect information about your environment, such as temperature and pressure, and communicate it to the brain. They also relay signals from the brain telling your muscles to move.

Structure

The nerves that extend away from the spine and into your limbs are part of the peripheral nervous system. They send signals to and from the central nervous system, which is made up of your brain and the nerves of the spinal cord.

The femoral nerve is a peripheral nerve. It is one of the largest nerves in the human body.

Location

The femoral nerve combines nerve fibers that emerge from between the second, third, and fourth lumbar (lower back) vertebrae. As it extends downward, it branches off to the skin, muscles, and connective tissues of the hip and thigh, including the iliacus muscle (a thigh flexor) and the inguinal ligament (in the groin).

It then crosses the hip joint and enters the femoral region of the thigh before splitting into two nerve trunks, which are called the anterior (front) and posterior (rear) divisions. From there, it divides into numerous smaller branches through the front and inside of the thigh.

The anterior femoral nerve then connects to several muscles, including pectineus and sartorius muscles. The posterior branch travels to the four quadriceps.

The anterior and posterior nerves both have branches that provide sensation to the skin. In the posterior branch, the primary one is the saphenous nerve, which extends down the lower leg and into the foot.

Function

The femoral nerve handles several important functions, both motor (having to do with movement) and sensory (having to do with feeling).

Motor Function

The motor functions of the femoral nerve are crucial to basic functionality such as standing, walking and running. This nerve flexes the hip joint via the pectineus, iliacus, and sartorius muscles, which is what allows you to lift your leg to take a step.

It also extends (straightens) the knee via the quadriceps, which includes the following muscles: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. In addition, the rectus femoris also helps stabilize the hip joint and assists in flexing the thigh.

Sensory Function

The anterior femoral nerve's cutaneous (skin) branches and the saphenous nerve allow you to feel pressure, pain, temperature, and other sensations along the front and inner portions of your thigh and inside of the lower leg and the foot.

Associated Conditions

Femoral nerve dysfunction can occur when the nerve is compressed, entrapped, or damaged. These problems can be the result of numerous things, including:

• Injury, especially if the femoral vein is also damaged and there's internal bleeding
• A tumor that puts pressure on the nerve
• Abnormal blood vessels
• Pelvis bone fractures
• A complication of catheterizing the femoral artery, which is right next to the nerve where it passes through the groin, which is necessary for certain surgical procedures
• Diabetic neuropathy (pain from nerve damage) or other peripheral neuropathy
• Internal bleeding or hemorrhage the lower abdomen
• Wearing tight or heavy belts

Common symptoms of femoral nerve dysfunction are:

• Burning or tingling that may be painful in the thigh, knee, or leg
• Decreased sensation or numbness in the thigh, knee, or leg (most common on the front and inside of the thigh, but sometimes even in the foot or feet)
• Weakness in the knee or leg, or feeling of the knee giving out, especially when going down stairs
• A dull ache in the genital region
  

To evaluate these symptoms in your leg(s), your healthcare provider will perform a comprehensive physical exam looking for:

• Weakness when straightening your knee
• Weakness when you bend at the hip
• Sensation changes in the front of the leg
• Abnormal knee reflex
• Shrunken quadriceps muscles

They may also check muscles related to other nerves to determine whether only the problem is confined to the femoral nerve or more widespread.

They may also order tests, including:

• Nerve conduction tests: This test measures how fast electrical impulses flow through your nerves. Slow signals generally indicate nerve damage.
• Electromyography (EMG): This test is typically done just after the nerve conduction test. It records the electrical activity in your muscles when the nerves are active and can tell your healthcare provider how your muscles and nerves are working together. It also can distinguish a muscle-based problem from a nerve problem.
• Magnetic resonance imaging (MRI): This scan uses magnets and radio waves to look for tumors or other growths that could be compressing the nerve.
• Computerized tomography (CT) scan: This scan can identify bone growths and problems with your veins.

Depending on your symptoms, your healthcare provider may also order X-rays and/or blood tests.

Treatment

For many of those problems, the first step is treating the condition that's causing the nerve problem, such as:

• Surgery to remove tumors/growths that are compressing the nerve
• Weight loss and lifestyle changes, if diabetes or weight are an underlying cause

Other problems, such as inflammation from an injury, may go away on their own.

Pain and weakness can lead to inactivity, which can cause your muscles to shrink and atrophy. Physical therapy may help you regain lost function or prevent loss of function.

In some cases, people have long-term disability due to losing some or all sensation. The resulting muscle weakness may lead to falls, which can cause injuries, especially in older people.

Another possible complication is the inability to notice injuries because of sensation loss, meaning the injuries aren't treated properly. That can lead to further damage or—in the case of cuts, scrapes, and burns—infection.

If you start having symptoms of femoral nerve dysfunction, especially after an injury, be sure to get medical help.