Sudden leg weakness can be a sign of a serious underlying health issue and should be evaluated by a doctor as soon as possible. In some cases, it may indicate a medical condition that requires emergency care.

Here we’ll discuss some common causes of leg weakness and other symptoms you need to know.


A stroke occurs when the blood supply to your brain is cut off because of a blockage, or a blood vessel in the brain bursts. It can cause sudden numbness or weakness in the face, arms, or legs.

Other signs and symptoms of stroke include:

  • sudden confusion
  • difficulty speaking
  • sudden, severe headache
  • drooping of one side of the face or uneven smile

If you or someone else is having a stroke, call 911 immediately. Prompt treatment is vital to recovering from a stroke. Early treatment can reduce the risk of long-term complications.

Multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system. In MS, your immune system attacks the myelin, which is the protective sheath around your nerves. It’s most often diagnosed in people aged 20 to 50.

MS can cause a wide range of symptoms that vary from person to person. Numbness and fatigue are the most common symptoms. Other symptoms include:

  • muscle weakness
  • muscle spasticity
  • difficulty walking
  • tremors
  • acute and chronic pain
  • visual disturbances

MS is a lifelong condition that can include periods of relapses of symptoms that are followed by periods of remission, or it can be progressive.

Treatments for MS, including medication and physical therapy, can help you regain strength in your legs and slow progression of the disease.

Pinched nerve

Sciatica, which is caused by a pinched nerve in the lower back, is pain that radiates along the sciatic nerve, which extends from your lower back through your hips and buttocks and down the legs. It usually affects one side of your body.

Sciatica can range from a dull ache to sharp burning pain, and worsen with prolonged sitting or sneezing. You may also experience leg numbness and weakness.

Mild sciatica usually goes away with rest and self-care measures, such as stretching. See your doctor if your pain lasts longer than a week or is severe.

Get emergency care if you experience sudden, severe pain in your lower back or leg accompanied by muscle weakness or numbness, or trouble controlling your bladder or bowels, which is a sign of cauda equina syndrome.

Spinal lesion or tumor

A spinal lesion or tumor is an abnormal growth of tissue within or surround the spinal cord or column. Spinal tumors can be cancerous or noncancerous, and originate in the spine or spinal column or spread there from another site.

Back pain, which is worse at night or increases with activity, is the most common symptom. If the tumor presses on a nerve, it can cause numbness or weakness in the arms, legs, or chest.

Treatment depends on the type and location of the lesion or tumor, and whether or not it’s cancerous or noncancerous. Surgery to remove the tumor, or radiation therapy or chemotherapy to shrink the tumor, can usually resolve leg weakness.


Toxic neuropathy is nerve damage caused by toxic substances, such as cleaning chemicals, insecticides and pesticides, and lead. Drinking a lot of alcohol can also cause it. This is called alcoholic neuropathy.

It affects the nerves of your arms and hands or legs and feet, causing nerve pain, numbness or tingling, and weakness that can lead to loss of movement.

Treatment involves medication to relieve nerve pain and limiting exposure to the toxin.

When to see a doctor

Leg weakness should always be evaluated by a doctor as it may be caused by a serious underlying condition that requires treatment.

Get emergency medical care if:

  • Your weakness is accompanied by sudden, severe pain in your back or leg.
  • You experience loss of bladder or bowel control.
  • You or someone else experiences any warning signs of a stroke.

The bottom line

Sudden leg weakness could be a sign of a serious medical issue, such as a stroke. Head to the nearest emergency room or call 911 if you’re not sure what’s going on.

Other conditions can also cause leg weakness or difficulty walking. See your doctor as soon as possible if you experience leg weakness, numbness or tingling, or changes to how you walk.