The causes of arm muscle pain are numerous. According to MayoClinic.com, arm pain can manifest anywhere from the the shoulder to the wrist. Arm pain may be caused by any of the structures that compose the arm, including bones, nerves, muscles, tendons and ligaments. In some cases, arm muscle pain may be caused by problems outside the arm, such as problems in the neck, shoulder or wrist. Arm muscle pain ranges in severity from mild to severe.
Bicipital Tendinitis
Bicipital tendinitis can cause arm muscle pain. According to the U.S. National Library of Medicine and the National Institutes of Health or NIH, tendinitis, including bicipital tendinitis, is characterized by inflammation, irritation and swelling of a tendon. The NIH notes that, in many cases, tendinosis or degenerative changes are also present in the tendon. Tendons are thick, fibrous bands of tissue that link muscle with bone. The bicipital tendon joins the long head of the biceps brachii muscle--one of the prominent muscles of the upper arm--with the supraglenoid tubercle of the scapula or shoulder blade. The bicipital tendon runs across the head of the humerus or arm bone through a groove. Overuse, trauma and aging can cause bicipital tendon problems and arm muscle pain to manifest in this area of the upper arm. Common signs and symptoms of bicipital tendinitis or tendinosis include pain and tenderness along the bicipital tendon, night pain in the affected area and pain that's worse when the upper arm and shoulder are moved through certain ranges of motion.
Thoracic Outlet Syndrome
Thoracic outlet syndrome can cause arm muscle pain. The National Institute of Neurological Disorders and Stroke or NINDS--a division of the National Institutes of Health--states that thoracic outlet syndrome is a general term that describes compression or impingement of nerves or blood vessels in the neck, shoulder and arm that causes pain, numbness or tingling in the arm and forearm muscles. Most physicians believe that thoracic outlet syndrome is caused by compression of the brachial plexus--a group of nerve roots or spinal cord offshoots--or subclavian blood vessels as they course through the base of the neck to the armpit and arm. Compression of these structures may be caused by tight neck and shoulder muscles or by an extra rib. Common signs and symptoms associated with thoracic outlet syndrome include pain, numbness, tingling and heaviness in the arm on the affected side. Thoracic outlet syndrome can occur on one or both sides of the body. This condition usually responds well to conservative care methods.
Muscle Contusion
A muscle contusion or bruising of the arm muscles can cause arm muscle pain. According to the American Academy of Orthopaedic Surgeons, muscle contusions are caused by blunt-force trauma and are particularly common among athletes, especially athletes that participate in contact sports, such as hockey, rugby and football. In fact, the AAOS states that contusions are the second most common cause of sports injuries, behind muscle strains. Muscle contusions of the upper arm are characterized by bruising of the skin, muscles--primarily the biceps and triceps--and underlying tissues. Arm contusions cause bleeding in the affected area, due to the breakage of small, superficial blood vessels known as capillaries. The rupture of capillaries allows blood to seep into muscles, tendons and other soft tissues in the affected area, which causes discomfort and tissue discoloration. According to the AAOS, a person with an upper arm contusion may develop a lump or hematoma over the injury site.
