Upper arm muscle pain can significantly impact your daily activities. The cause of your pain may be easy to determine, particularly if you experienced a traumatic injury or recently worked out at the gym. However, other causes of upper arm muscle pain, such as shoulder injuries, nerve compression or medical conditions including cancer, stroke or heart attack, may not be immediately apparent. See your doctor for an accurate diagnosis if you have upper arm muscle pain.
Muscle strain is a likely cause of upper arm muscle ache. This injury occurs when a muscle is overstretched. Muscle strains range in severity; there may be very little muscle tissue damage, or there may be tearing of the muscle fibers. Mild strains may heal within 1 to 3 days, while severe strains may take a few months to heal. Upper arm muscle strains may occur with heavy lifting or repetitive use of your arm. Pain from these strains typically increases with activity and decreases with rest. Severe strains may cause bruising on the skin of your upper arm.
Inflammation of your shoulder joint or the tendons that move your shoulder may cause aching in your upper arm muscles. This pain -- called referred pain -- is typically felt along the outer muscles in your upper arm, not in your shoulder where the injury actually occurred. The most common cause of this type of pain is shoulder impingement -- pinching of structures between the bones in your shoulder. This condition may develop from repetitive overhead work, sports activities or prolonged poor posture. Pain in your upper arm typically increases with activity and may decrease with rest. These shoulder injuries are often successfully treated with physical therapy.
Nerves exit your spine between each of your vertebrae, which are the bones that make up your spine. Cervical spinal nerves exit the vertebrae in your neck, supplying sensation to the skin and power to the muscles in your arms and hands. The spinal nerve C5 supplies sensation to your upper arm. This nerve can be compressed by bulging discs that provide padding between the bones in your spine, or by narrowing of the holes through which the nerves exit. C5 nerve compression can cause pain in your upper arm, usually along the outer border. Neck pain may or may not be present with this condition. Placing your arm over your head may decrease upper arm pain caused by cervical nerve impingement.
Less commonly, upper arm muscle pain may be caused by underlying medical conditions such as stroke or heart attack. These conditions may be life-threatening and are typically accompanied by other symptoms, such as numbness or tingling on one side of the body, weakness, slurred speech, chest pain or pressure, dizziness or pain that radiates to your jaw. Upper arm muscle pain may also be caused by cancerous or non-cancerous tumors. Other signs of cancer might include unexplained weight loss, fatigue and loss of appetite. Seek immediate medical attention if you have arm pain accompanied by any of these symptoms.