Causes of Upper Arm Muscle Pain

Even simple, everyday activities can be difficult when a muscle in your upper arm aches. The cause of your pain may be relatively obvious, particularly if your pain started suddenly in association with a traumatic injury or recent heavy lifting.

Other causes of upper arm muscle pain, such as a shoulder injury, nerve compression or other medical conditions, may not be as readily apparent.

Read more: 10 Ways to Tell Good Pain From Bad Pain

Strain Injury

A strain injury is a common cause of upper arm muscle achiness. This injury occurs when a muscle and/or its associated tendon is overstretched, leading to tearing of the fibers. Strain injuries range from mild to severe, depending on the extent of tearing. A complete tear, or rupture, is the most severe type of strain injury.

Pain associated with a strain occurs immediately or shortly after the injury, which helps differentiate this condition from simple muscle soreness. Activity that involves use of the affected muscle aggravates the pain and rest reduces it.

Other symptoms might also include swelling, stiffness, muscle cramps or spasms, and possibly bruising with more serious strains. Mild strains typically heal within 2 to 3 weeks. Complete healing with a more serious strain can take up to 2 to 3 months. Upper arm strains usually occur due to heavy lifting or overuse of a fatigued muscle.

Shoulder Injury

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Inflammation of your shoulder joint and/or the associated tendons may trigger achiness in your upper arm muscles. This pain is typically felt in the outer muscles of your upper arm. The most common cause of this type of pain is shoulder impingement, which involves pinching of the structures between the bones in your shoulder.

Pain in your upper arm typically increases with activity and might decrease with rest. Nighttime pain often occurs with shoulder impingement and there might be limited mobility of the shoulder joint. This condition usually develops due to repetitive overhead work, sports activities or prolonged poor posture with the shoulders rolled forward.

Nerve Compression

Nerves exit your spinal cord between each of your vertebrae, the bones of your spine. Cervical spinal nerves exit between the vertebrae in your neck. They supply sensation to the skin and power to the muscles of your arms and hands. The spinal nerve C5 supplies sensation to your upper arm. This nerve can be compressed by a bulging intervertebral disc, a structure that provides padding between the vertebrae.

Arthritis-related bone changes in the neck can also lead to C5 nerve compression. This condition frequently causes pain in the outer aspect of the upper arm. Neck and shoulder pain might also be present. Placing the hand of the affected arm on top of the head might decrease upper arm pain caused by C5 nerve compression.

Read more: How to Relieve Arm Pain Caused by a Pinched Nerve

Humerus Fracture

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A break in your upper arm bone, the humerus, can cause achiness that you might assume is coming from your muscles. While a traumatic humerus fracture is usually obvious after a fall or forceful blow to your upper arm, the symptoms of a break in this bone can sometimes be subtle.

Hairline stress fractures of the humerus can occur if you frequently play overhead sports — those that involve forceful overhead arm motions, such as tennis, racquetball, handball, volleyball and baseball pitching. Symptoms include progressively increasing upper arm pain with overhead use and achiness at rest.

Other Conditions That Cause Pain in the Upper Arm

Upper arm pain that seems to be arising from muscle can occur with several other conditions, including:

• An infection of the humerus
  
• A noncancerous or cancerous tumor of the humerus
• A blood clot in an upper arm vein
• Heart attack 

Read more: 10 Drug-Free Solutions for Every Type of Pain

When to See a Doctor

See your doctor for an accurate diagnosis if you experience upper arm muscle pain. Seek urgent medical care if your arm pain started in association with a traumatic injury, such as a hard blow to your arm or a fall. Seek emergency medical care if your arm pain is accompanied by any warning signs or symptoms, including:

• Difficulty breathing or shortness of breath
• Chest tightness or pain
• Dizziness, lightheadedness or fainting
• Sudden numbness or tingling
• Weakness or paralysis
• Difficulty speaking or understanding others' speech
• A sudden vision change in one or both eyes
• Difficulty walking, loss of balance or poor coordination

Reviewed and revised by: Tina M. St. John, M.D.