Leg Weakness

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What is leg weakness?

Leg weakness can occur as part of a generalized feeling of weakness all over your body, or it may develop in one or both legs. True weakness occurs when the muscles lose their strength, but people often perceive that their muscles are weak when they feel ill or tired. In these cases there is not a true loss of muscle function. The sudden onset of muscle weakness can be a sign of stroke, a potentially life-threatening condition in which part of the brain is deprived of oxygen.

This article focuses on conditions that cause a true loss of strength in the leg muscles. Among the most common causes for leg weakness is sciatica, problems with the spinal cord that lead to pinching or compression of the nerves as they exit the spinal cord through the holes between the vertebrae of the backbone. Sciatica may be caused by various conditions. In addition to weakness in one part of the arm or leg, other symptoms such as tingling, burning or pain may occur.

Neuromuscular diseases, such as myasthenia gravis (autoimmune neuromuscular disorder that causes muscle weakness) and multiple sclerosis (disease that affects the brain and spinal cord causing weakness, coordination, balance difficulties, and other problems), are other causes for muscle weakness that can occur in the legs. Toxins such as botulinum toxin and certain medications can also cause muscle weakness.

Leg weakness of sudden onset can be a sign of stroke, a potentially life-threatening situation. Seek immediate medical care (call 911) for leg weakness that comes on suddenly, particularly if it is felt on one side of the body or is accompanied by any serious symptoms, including blurred vision or double vision, loss of vision, or changes in vision; numbness; paralysis or inability to move a body part; severe headache; high fever (higher than 101 degrees Fahrenheit); loss of bladder or bowel control; fainting or change in level of consciousness; or lethargy.

If your leg weakness persists or causes you concern, seek prompt medical care.

What other symptoms might occur with leg weakness?

Leg weakness may accompany other symptoms, which vary depending on the underlying disease, disorder or condition. Symptoms that frequently cause leg weakness may also involve other body systems.

Leg symptoms that may occur along with leg weakness

Leg weakness may accompany other symptoms affecting the leg including:

  • Burning feeling

  • Muscle spasms

  • Numbness

  • Paralysis

  • Pins-and-needles (prickling) sensation

  • Redness, warmth or swelling

  • Twitching

Other symptoms that may occur along with leg weakness

Leg weakness may accompany symptoms related to other body systems including:

  • Back pain

  • Body aches

  • General ill feeling

  • Hand, arm or finger pain

  • Headache

  • Impaired balance and coordination

  • Loss of muscle coordination

  • Symptoms of multiple sclerosis such as weakness, numbness or tingling, vision problems, unsteady walk, fatigue, and depression

  • Tingling or other unusual sensations in the hands or feet

Serious symptoms that might indicate a life-threatening condition

In some cases, leg weakness may be a symptom of a life-threatening condition that should be immediately evaluated in an emergency setting. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms including:

  • Changes in hearing, taste or smell

  • Confusion

  • Fainting or change in level of consciousness or lethargy

  • High fever (higher than 101 degrees Fahrenheit)

  • Impaired balance and coordination

  • Loss of vision or changes in vision

  • Progressive weakness and numbness in the legs

  • Severe headache

What causes leg weakness?

Leg weakness can be caused by any kind of injury, neuromuscular diseases, toxins, or life-threatening illnesses such as stroke.

Spinal causes of leg weakness

Conditions that affect the spinal cord, the backbone (vertebrae) or the nerves that exit from the spinal cord can all cause leg weakness along with pain, burning, numbness or a tingling sensation along the course of the nerve that is affected. Examples include:

Traumatic causes of leg weakness

Injury to the bones, muscles or joints is known to cause leg weakness. Examples include:

  • Fractures of bone

  • Sprains and strains

Neuromuscular causes of leg weakness

A number of conditions that affect the muscles or nerves in the body can produce leg weakness. These conditions include:

  • Amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig’s disease; severe neuromuscular disease that causes muscle weakness and disability)

  • Cerebral palsy (disordered brain function that leads to a variety of neuromuscular symptoms)

  • Fibromyalgia (chronic condition that causes pain, stiffness and tenderness)

  • Guillain-Barre syndrome (autoimmune nerve disorder)

  • Multiple sclerosis (disease that affects the brain and spinal cord, causing weakness, coordination and balance difficulties, and other problems)

  • Muscle breakdown (rhabdomyolysis)

  • Muscular dystrophy (inherited disorder that causes progressive loss of muscle tissue and muscle weakness)

  • Myasthenia gravis (autoimmune neuromuscular disorder that causes muscle weakness)

  • Polymyositis (widespread inflammation and weakness of muscles)

Toxins and drugs that cause leg weakness

Certain toxins and medications may cause muscle weakness including:

  • Botulinum toxin

  • Medications such as statins (to lower cholesterol) and corticosteroids

  • Organophosphate poisoning

Serious or life-threatening causes of leg weakness

In some cases, leg weakness, particularly if it has a sudden onset and is localized to one side of the body, may be a sign of stroke, a life-threatening condition that should be immediately evaluated in an emergency setting. Life-threatening causes of leg weakness include:

  • Stroke

  • Transient ischemic attack (temporary stroke-like symptoms that may be a warning sign of an impending stroke)

Questions for diagnosing the cause of leg weakness

To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your leg weakness including:

  • How long have you felt your leg weakness?

  • In which part of the leg does the weakness occur?

  • Have you injured your leg recently?

  • Do you have any other symptoms?

  • What medications are you taking?

What are the potential complications of leg weakness?

Because leg weakness can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:

  • Brain damage

  • Disability

  • Nerve problems that cause pain, numbness or tingling

  • Paralysis

  • Permanent or chronic pain

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2018 Dec 28
  1. Sciatica. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/000686.htm
  2. Stroke. PubMed Health, a service of the NLM from the NIH. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001740/
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