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
“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.
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
Systemic Health Conditions
Some relatively rare causes of leg numbness include the following conditions:
- Multiple sclerosis (MS)
- Vitamin deficiencies, especially vitamin B12
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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