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 11 common causes of leg weakness and other symptoms you need to know.

A slipped disc occurs when the gelatinous substance inside the discs that cushion your vertebrae protrudes through a tear in the exterior, causing pain. This can happen because of injury or age-related degenerative changes in the spine.

If the slipped disc compresses a nearby nerve, it can cause pain and numbness along the affected nerve, often down your leg.

Other symptoms include:

See your doctor if neck or back pain extends down your arm or leg or you experience numbness, tingling, or weakness. Conservative treatment, including rest followed by physical therapy, usually relieves symptoms within a few weeks.

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:

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.

Guillain-Barré syndrome is a rare autoimmune disorder in which your immune system attacks your nerves, causing tingling and weakness that usually begins in the feet and legs. The weakness can spread quickly and eventually paralyze the whole body if not treated right away.

Other symptoms can include:

  • prickling or pins and needles sensations in your wrists, fingers, ankles, and toes
  • severe pain that worsens at night
  • difficulty with eye or facial movements
  • problems controlling your bladder or bowels

The cause of the condition isn’t known, but it’s often triggered by an infection, such the stomach flu or a respiratory infection.

See a doctor right away if you experience any of these symptoms. There’s no cure, but there are treatments that can relieve symptoms and reduce the duration of the illness.

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:

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.

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.

Peripheral neuropathy is nerve damage to your body’s peripheral nervous system, which connects the nerves from your central nervous system to the rest of your body.

It can be caused by injury, infection, and a number of conditions, including diabetes (diabetic neuropathy) and hypothyroidism.

Symptoms usually start with numbness or tingling in the hands and feet, but can spread to other parts of your body. Other symptoms include:

  • weakness
  • pain that worsens at night
  • burning or freezing sensation
  • shooting or electric-like pain
  • difficulty walking

Treatment depends on the cause of the nerve damage and may begin with treating an underlying condition. Prescription medications and different therapies are also available.

Parkinson’s disease is a neurodegenerative disorder that affects an area of the brain called the substantia nigra.

Symptoms of the condition develop gradually over the years. Problems with movement are usually the first signs. Other Parkinson’s disease symptoms include:

  • small handwriting or other writing changes
  • slow movement (bradykinesia)
  • limb stiffness
  • problems with balance or walking
  • tremors
  • voice changes

Treatment for Parkinson’s disease involves a combination of lifestyle changes, medications, and therapies. Medications and physical therapy can help reduce muscle loss caused by Parkinson’s disease.

Myasthenia gravis (MG) is a neuromuscular disorder that causes weakness in your voluntary skeletal muscles. It can affect people of any age, but is more common in women under the age of 40 and men older than 60.

Symptoms include:

There’s no cure for MG, but early treatment can limit disease progression and help improve muscle weakness. Treatment is typically a combination of lifestyle changes, medications, and sometimes surgery.

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.

Amyotrophic lateral sclerosis (ALS) is also known as Lou Gehrig’s disease. It’s a progressive neurological disease that damages nerve cells and often begins with muscle twitching and weakness in the legs.

Other early symptoms include:

  • difficulty walking or performing daily tasks
  • trouble swallowing
  • slurred speech
  • difficulty holding up your head

There’s currently no cure for ALS, but treatments are available that can help control symptoms and complications and improve quality of life.

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.

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.

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.