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:

  • Anemia (low red blood cell count)
  • Electrolyte imbalance
  • Fibromyalgia (chronic condition that causes pain, stiffness and tenderness)
  • Heavy metal poisoning such as lead poisoning
  • Malnutrition
  • Thyroid problems
  • Toxic ingestion, such as eating poisonous plants, mushrooms or chemicals

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


  1. Stroke. PubMed Health. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001740/.
  2. Weakness. MedlinePlus, A service of the U.S. National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003174.htm.
  3. Bope ET, Kellerman RD (Eds.) Conn’s Current Therapy.Philadelphia: Saunders, 2012.

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 h... Read more about arm weaknessintroduction


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:

Medical Reviewer: William C. Lloyd III, MD, FACS Last Annual Review Date: Aug 9, 2013 Copyright: © Copyright 2014 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

This Article is Filed Under: Bones, Joints and Muscles

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