Arm Weakness

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is arm weakness?

Arm weakness refers to a loss of strength in the arm and the inability to move an arm because of decreased muscle strength. It can happen spontaneously or progress slowly over time. Weakness in the arm may occur on one or both sides of the body, may accompany weakness in other parts of the body, and may occur with a variety other symptoms, including arm pain. If you have arm weakness, you may have difficulty simply moving the affected arm, or you may have difficulty performing daily tasks.

In some cases, physical therapy may help to improve arm strength. If arm weakness occurs with pain, pain medication may assist in resolving both symptoms. Optimal treatment for arm weakness is dependent on the underlying cause of the weakness.

Usual causes of arm weakness include injury to, or infection of, the arm; muscle wasting, such as from certain muscular disorders or from lack of use; nerve damage or compression at the vertebral column; or certain hereditary conditions. Stroke is a serious and potentially life-threatening cause of sudden arm weakness that appears on one side of the body – a true medical emergency. Temporary arm weakness may be caused by a general infection, such as the common cold.

While arm weakness is generally not serious, arm weakness can be a sign of stroke. Seek immediate medical care (call 911) if you experience serious symptoms that may indicate a stroke, such as a sudden, severe headache; loss of consciousness; confusion; sudden numbness or paralysis, especially if it occurs on one side of the body; vision changes, or difficulty speaking.

If your arm weakness is persistent or causes you concern, seek prompt medical care.

What other symptoms might occur with arm weakness?

Arm weakness may accompany other symptoms, which vary depending on the underlying disease, disorder or condition.

Musculoskeletal symptoms that may occur along with arm weakness

Arm weakness may accompany other symptoms affecting the musculoskeletal system including:

Neurological symptoms that may occur along with arm weakness

Arm weakness may accompany other symptoms affecting the nervous system (brain, nerves, and spinal cord) including:

  • Confusion or loss of consciousness
  • Difficulty chewing, swallowing or speaking
  • Muscle spasms
  • Numbness or tingling
  • Paralysis

Other symptoms that may occur along with arm weakness

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

Serious symptoms that might indicate a life-threatening condition

In some cases, arm weakness may be a symptom of a life-threatening condition, such as a stroke or serious infection, that should be evaluated immediately 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:

  • Change in level of consciousness or alertness, such as passing out or unresponsiveness
  • Garbled or slurred speech
  • High fever (higher than 101 degrees Fahrenheit)
  • Paralysis or inability to move a body part
  • Sudden weakness, numbness, or tingling on one side of the body
  • Vision changes or vision loss
  • Worst headache of your life

What causes arm weakness?

Arm weakness can arise from a variety of events or disorders that affect the muscles, bones, joints, nervous system, or metabolism. Arm weakness can be accompanied by more generalized weakness, such as is common with certain hereditary disorders, or it may be the result of a specific injury to the arm.

Musculoskeletal causes of arm weakness

Arm weakness may be caused by damage to the muscles or bones of the arm or certain muscular and skeletal diseases including:

  • Arm injury
  • Arthritis
  • Cyst (benign sac that contains fluid, air, or other materials)
  • Fractured or broken bone
  • Infection of the soft tissues of the arm
  • Muscular dystrophy (inherited disorder that causes a progressive loss of muscle tissue and muscle weakness)
  • Myopathy (muscle disease that results in muscle weakness)
  • Tendinitis (inflammation of a tendon)

Neurological causes of arm weakness

Arm weakness can also be caused by problems with the nervous system including:

  • Amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig’s disease; severe neuromuscular disease that causes muscle weakness and disability)
  • Carpal tunnel syndrome
  • Cerebral palsy (group of disorders that impair movement, balance and posture)
  • Multiple sclerosis (disease that affects the brain and spinal cord causing weakness, coordination, balance difficulties, and other problems)
  • Myasthenia gravis (autoimmune neuromuscular disorder that causes muscle weakness)
  • Nerve entrapment or compression, such as of the ulnar nerve in the arm
  • Radiculopathy (compression of a nerve in the spine)
  • Severed nerve

Other causes of arm weakness

Arm weakness can also be caused by a variety of systemic conditions including:

Serious or life-threatening causes of arm weakness

In some cases, arm weakness may be a symptom of a serious or life-threatening condition that should be evaluated immediately in an emergency setting. These include:

  • Brain tumor
  • Severe infection, accompanied by high fever (higher than 101 degrees Fahrenheit)
  • Stroke
  • Transient ischemic attack (temporary stroke-like symptoms that may be a warning sign of an impending stroke)

Questions for diagnosing the cause of arm weakness

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

  • How long have you felt weakness in your arm?
  • Do you have any other symptoms?
  • Have you had any recent infections?
  • Have you had any recent injuries?
  • Do you have a family history of autoimmune disorders, such as multiple sclerosis?

What are the potential complications of arm weakness?

Arm weakness itself is not usually a serious condition. Mild arm weakness may be temporary and may resolve spontaneously. Because arm weakness can be due to serious diseases, however, 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:

  • Paralysis
  • Permanent loss of coordination
  • Permanent loss of sensation
  • Spread of cancer
  • Spread of infection
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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Dec 5
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Stroke. PubMed Health, a service of the NLM from the NIH.
  2. Weakness. MedlinePlus, A service of the U.S. National Library of Medicine National Institutes of Health.
  3. Bope ET, Kellerman RD (Eds.) Conn’s Current Therapy. Philadelphia: Saunders, 2012