Pain felt in the upper left back is often localized to the thoracic spine region, specifically the vertebrae labeled T1 through T6, which anchor the upper rib cage. This particular area is a convergence point for muscles, nerves, and the underlying structures that protect vital organs like the heart and left lung. Pinpointing the exact cause of discomfort in this location can be complex because pain signals from various tissues—muscles, bones, and even internal organs—can be perceived in the same vague area. The discomfort can range from a dull ache to a sharp, burning sensation, and understanding the potential sources is the first step toward finding relief.
Musculoskeletal Sources of Pain
The most frequent causes of upper back pain originate in the muscles and other soft tissues supporting the shoulder blades and spine. Muscle strain, or a tear in the muscle fibers, commonly affects the rhomboids (between the spine and shoulder blade) or the large trapezius muscle. These strains often result from sudden, forceful movements or repetitive actions, such as carrying a heavy bag on one shoulder or improper lifting technique.
Poor posture is another primary culprit, especially for individuals who spend long periods seated at a desk with a rounded upper back. This sustained slouching places chronic tension on the muscles and ligaments, leading to fatigue, stiffness, and eventual muscle spasms. This constant strain can also contribute to myofascial pain syndrome, characterized by trigger points. These trigger points, often described as “knots,” are hyperirritable spots within the muscle tissue that cause local pain or refer pain to other areas, often manifesting as a deep ache in the upper left back.
Structural and Neurological Causes
Beyond muscle tissue, the bony architecture of the thoracic spine and its associated nerves can be the source of pain. Issues involving the thoracic vertebrae, such as disc bulges or degeneration, can irritate the nerves exiting the spinal column (thoracic radiculopathy). Though less common than in the lower back, a thoracic herniated disc can put pressure on a nerve, causing sharp or shooting pain that radiates around the rib cage or shoulder blade.
The ribs articulate with the thoracic vertebrae and can become misaligned or irritated at the joint. Costochondritis, an inflammation of the cartilage connecting the ribs to the breastbone, can sometimes cause sharp pain felt in the back rather than the chest. This pain may worsen with deep breaths or movements that engage the rib cage.
Nerve compression can also occur outside the spine, such as in thoracic outlet syndrome, where nerves or blood vessels are compressed between the collarbone and the first rib. While primarily affecting the arm and hand, this compression can sometimes produce pain that begins in the upper back and radiates outwards. Degenerative changes, such as facet joint arthritis, can also narrow the space where nerves exit, leading to chronic neurological discomfort.
Referred Pain from Internal Organs
Referred pain originating from internal organs (visceral pain) is a possibility with upper left back discomfort. The nervous system sometimes misinterprets pain signals, projecting the sensation to an unrelated area like the back. Since the heart and left lung are located in the chest cavity, conditions affecting these organs can manifest as discomfort in the upper left back.
Cardiovascular issues, such as angina or a heart attack, can cause pain that radiates to the left shoulder blade, neck, or jaw, rather than the classic chest pressure. This occurs because the sensory nerves from the heart and the upper back enter the spinal cord at similar levels. Any sudden, unexplained back pain accompanied by symptoms like shortness of breath, lightheadedness, or sweating warrants immediate medical evaluation.
Pulmonary conditions are also potential sources of referred pain. Pleurisy, inflammation of the lining surrounding the lungs, causes sharp chest pain that often worsens with deep breathing, coughing, or sneezing, and can be felt in the upper back. A pulmonary embolism, a blockage in a lung artery, is a serious condition that presents with sudden, sharp back pain along with difficulty breathing.
Gastrointestinal issues can occasionally refer pain to this area. Conditions affecting the stomach or esophagus, such as severe acid reflux or an ulcer, may sometimes be perceived as back pain. Additionally, disorders of the spleen, located under the left rib cage (e.g., enlargement or rupture), can cause pain in the left upper abdomen that radiates to the left shoulder and back.
Identifying Red Flag Symptoms
While most upper left back pain is musculoskeletal and resolves with conservative care, certain accompanying symptoms are considered “red flags” that require immediate medical attention. The most urgent symptoms involve signs of cardiac, pulmonary, or severe neurological compromise. Any pain accompanied by chest pressure, difficulty breathing, or a sudden onset of weakness should be treated as an emergency.
Symptoms signaling a potentially serious underlying condition include back pain that is constant, worsens at night, or is not relieved by rest. Unexplained weight loss, fever, or chills may suggest an infection or systemic illness. Neurological red flags include new numbness, tingling, or weakness radiating down the arm or leg, or an inability to control bowel or bladder function. These signs indicate possible severe nerve or spinal cord compression that necessitates prompt diagnosis and treatment.