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The Causes of Leg Numbness

The Causes of Leg Numbness

Leg numbness can be caused by a range of common and rare health conditions, from diabetes to spinal deformities. These conditions may be related to nerves or circulation, or something else like an injury or lifestyle factors.

Nerve-Related Causes

The following nervous system conditions are common causes of leg numbness:

  • Peripheral neuropathy
  • Herniated disc
“Probably the most common cause of leg numbness is peripheral neuropathy,” says Ram Alluri, MD, an orthopedic surgeon at Keck Medicine of the University of Southern California in Los Angeles. Typically, this presents as numbness and other sensations, like burning or tingling, below the knee down through the foot, Dr. Alluri says. Peripheral neuropathy is caused by damage to small nerves, often due to diabetes. It can also occur due to other health conditions, chemotherapy treatments, or excessive alcohol consumption.

“With tingling and numbness below the knees, it can suggest diabetes,” especially if someone hasn’t been to the doctor in years, says Lukasz Jaros, MD, a family medicine physician at Northwestern Medicine in Chicago. In that case, Dr. Jaros says, he’ll order an A1C test to check for diabetes.

“As a spine surgeon, the most common reason I see leg numbness is a herniated disc,” says Alluri. This occurs when part of a disc in your spine, which acts as a cushion between bones, pushes out and presses against your spinal nerves. This can also cause leg pain when it affects certain nerves.

Another potential cause of leg numbness — along with pain — is sciatica, in which certain nerves running from your lower back to your legs become compressed or irritated.

 Sciatica pain often feels like burning or an electric shock, and tends to become more frequent over time, says Jaros.

A rare but serious cause of leg numbness can be a tumor, infection, or other abnormality that presses on nerves in the spinal cord itself. This may be the case when someone has pain shooting down both legs. “We would potentially be sending them to the emergency room for imaging and potentially a neurosurgical intervention” to prevent permanent spinal nerve damage, says Jaros.

Circulatory Causes

The following blood vessel conditions can cause leg numbness:

  • Peripheral arterial disease (PAD)
  • Deep vein thrombosis (DVT), a type of blood clot
Decreased blood circulation from peripheral arterial disease can make your leg feel numb or heavy, says Alluri. Typically, he says, a blood clot in your leg will cause redness and a warm or hot sensation, but it can also cause numbness in some people.

Systemic Health Conditions

Some relatively rare causes of leg numbness include the following conditions:

  • Multiple sclerosis (MS)
  • Vitamin deficiencies, especially vitamin B12
Typically, leg numbness in multiple sclerosis will be part of a range of symptoms, and will require specialized diagnosis and treatment. A vitamin B12 deficiency can be much easier to recognize and diagnose, often using a simple blood test.

Injury and Physical Factors

Certain other physical issues can cause leg numbness, especially:

  • Peripheral nerve compression
  • Injury or trauma
  • Positional nerve compression
Peripheral nerve compression occurs when a structure presses against a nerve below your spine, such as in your knee or ankle. This may occur due to arthritis, bone spurs, or something else. Any injury that causes nerve damage in your legs or feet can also cause numbness.

Sometimes, the positioning of your body — such as crossing your legs a certain way — can compress nerves and cause temporary numbness. In that case, sensation should return within a few minutes of adjusting your position. “If it happens once or twice, it’s usually not something that needs to be treated,” says Jaros.

Certain Medications

Some medications may cause numbness in your legs or arms by damaging small nerves. These drugs can include:

  • Heart and blood pressure drugs
  • Cancer or chemotherapy drugs
  • Certain infection-fighting drugs
  • Seizure treatments
  • HIV/AIDS treatments
Other toxic substances that may cause numbness include:

  • Arsenic
  • Illegal drugs
  • Glue sniffing

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