Pain localized to the left shoulder blade that is aggravated by breathing, particularly deep inhalation, often causes immediate concern. This discomfort is frequently described as a sharp, stabbing sensation that intensifies as the lungs expand. While the location can feel alarming, the pain may stem from a variety of sources, ranging from simple muscle strain to conditions involving internal organs. Understanding whether the pain originates in the musculoskeletal structure of the back or is “referred” from an internal organ is the first step toward determining the cause.
Musculoskeletal and Structural Causes
The most frequent source of left shoulder blade pain related to breathing involves the complex network of muscles, joints, and nerves in the upper back and neck. These structural causes are directly linked to movement and position, often worsening when the chest wall expands during a deep breath. A common culprit is a strain in the muscles responsible for stabilizing the shoulder blade, such as the rhomboids or trapezius, which are stretched and irritated during respiratory movements.
Poor posture, especially prolonged slouching while sitting, places undue stress on the thoracic spine and the surrounding musculature. This sustained tension can lead to muscle fatigue and trigger points that are sensitive to the movement of the rib cage during respiration. The pain from these muscle issues typically presents as a dull ache or tightness, but can become sharp with a maximal breath or when direct pressure is applied.
Issues in the cervical spine, or neck, can also refer pain down to the area between the shoulder blades. Conditions like a pinched nerve from a herniated or bulging disc in the lower neck can cause radicular pain perceived in the upper back. This nerve-related pain can be exacerbated by deep breathing or specific neck movements because the nerve roots may be irritated by the slight movement of the spine associated with chest expansion.
Costochondritis, an inflammation of the cartilage connecting the ribs to the breastbone, is another structural cause that can radiate pain to the back. Although the primary pain is often felt in the front of the chest, the inflammation can involve the rib joints near the spine, causing discomfort sensitive to chest wall movement. This pain is sharp and increases significantly with coughing, sneezing, or taking a deep breath. Musculoskeletal pain is generally distinguishable because it changes with body position or pressure, whereas referred pain from an organ often remains constant.
Internal Conditions Causing Referred Pain
Pain in the left shoulder blade that intensifies with breathing can be a manifestation of referred pain, indicating a problem originating in a thoracic or abdominal organ. Referred pain occurs because the internal organs and the muscles of the back share common nerve pathways that enter the spinal cord at the same level. The brain misinterprets the visceral signal as somatic pain coming from the more familiar location of the back or shoulder blade.
Conditions involving the lungs and the surrounding membranes are direct causes of pain tied to respiration. Pleurisy, the inflammation of the pleura (the tissue layers separating the lungs from the chest wall), is a prime example. When the inflamed layers rub against each other during inhalation, it causes a sharp, stabbing pain known as pleuritic chest pain, which can be felt in the left shoulder blade if the irritation is near the diaphragm.
More serious pulmonary conditions include pneumonia or a pulmonary embolism (PE), a blockage in the pulmonary arteries. In the case of PE, the pain is often sudden, severe, and sharp, and is directly linked to breathing because the clot can cause local tissue death and irritation of the pleura. The involvement of the diaphragm is important in referred pain, as it is innervated by the phrenic nerve, which originates from cervical spinal nerves C3, C4, and C5.
Abdominal issues affecting organs near the left side of the diaphragm can also refer pain to the left shoulder blade. An inflamed pancreas (pancreatitis) or an issue with the spleen, such as a rupture, can irritate the underside of the diaphragm. This irritation stimulates the phrenic nerve, and the brain interprets the signal as pain in the upper back and shoulder blade. Splenic injury referring pain to this area is sometimes called Kehr’s sign.
Cardiac events can also present with pain felt in the left shoulder blade or upper back, though they are typically associated with pain radiating down the left arm or to the jaw. Conditions like a heart attack, pericarditis (inflammation of the sac surrounding the heart), or an aortic dissection can cause referred pain. The nerves carrying pain signals from the heart enter the spinal cord at the same level as nerves from the upper back, leading to the mislocation of the pain. This type of referred cardiac pain may be constant, but it can be perceived as worsening during deep breathing due to the proximity of the heart to the chest wall.
Urgent Indicators and When to Seek Medical Help
While many causes of left shoulder blade pain when breathing are muscular and benign, the potential involvement of the heart or lungs means that certain accompanying symptoms should prompt immediate medical attention. Any pain in this area that is sudden, severe, or unexplained requires professional evaluation to rule out life-threatening conditions.
Urgent indicators include experiencing the pain along with:
- Shortness of breath.
- A feeling of chest tightness or pressure.
- Sudden onset of profuse sweating or dizziness.
- Pain that radiates into the left arm, jaw, or neck.
- Nausea, high fever, or chills.
- Coughing up blood.
These symptoms may signal a cardiac event, serious infection, or pulmonary issue requiring emergency care.
When evaluating this symptom, a physician will first perform a physical examination, checking the back, neck, and chest for tenderness that might point to a musculoskeletal origin. They will try to reproduce the pain through movement or pressure to help differentiate between structural and referred causes. If the pain is not reproducible with movement, internal causes are more strongly suspected.
To investigate internal causes, doctors typically order a series of diagnostic tests. These may include blood work to check for signs of infection or cardiac markers, a chest X-ray to look for signs of pneumonia, and an electrocardiogram (EKG) to assess heart function. Depending on the initial findings, a CT scan or an ultrasound may be used to get detailed images of the lungs, heart, or abdominal organs to pinpoint the exact source of the pain.