The pain felt beneath the left shoulder blade (scapula) is a common complaint, even though this area does not house any major internal organs. The sensation usually originates in the back muscles and joints, or it is perceived there through referred pain. Referred pain is a neurological phenomenon where nerve pathways from an internal structure converge with those from the skin and muscle at the spinal cord. This convergence causes the brain to misinterpret the source of the discomfort. Understanding the difference between local muscle strain and pain referred from deeper structures is important for determining the cause.
Local Causes: Musculoskeletal Pain
The most frequent source of pain directly beneath the left shoulder blade is a mechanical problem involving the surrounding muscles and the thoracic spine. A network of muscles, including the rhomboids and the trapezius, attach directly to the scapula. Strain or overuse of these muscle groups can create tender areas known as trigger points that produce a deep, aching sensation.
Poor posture, especially prolonged slouching, places chronic stress on the muscles and ligaments of the upper back. This sustained tension can lead to muscle fatigue and local inflammation, causing a persistent, dull ache. Dysfunction in the thoracic facet joints (the small joints connecting the vertebrae of the mid-back) can also generate pain that localizes directly adjacent to the scapula.
Nerve irritation in the cervical spine (neck) may also radiate pain downward to the shoulder blade area. A pinched nerve caused by a bulging disc, for example, can send sharp or burning sensations along the nerve root into the upper back. If the pain changes or worsens with specific movements of the neck or arm, it often points toward a structural or muscular origin.
Deeper Causes: Referred Pain from the Thorax
Pain perceived under the left shoulder blade can be a manifestation of a serious condition originating in the chest cavity. The heart, though located in the front of the chest, shares nerve pathways with the back, neck, and left arm. During a cardiac event, such as a heart attack, the resulting pain can be felt in the left scapular area instead of, or in addition to, classic chest discomfort.
This referred pain from the heart is often described as a squeezing pressure or a deep ache that does not change with movement or position. Conditions like angina (chest pain due to reduced blood flow to the heart muscle) can also present as pain radiating to the left shoulder blade. If this pain is accompanied by symptoms like shortness of breath, sweating, or chest pressure, seek immediate emergency medical attention.
The lungs and the pleura (the thin membrane lining the lungs and chest wall) can also refer pain to the back. Inflammation of the pleura, known as pleurisy, typically causes a sharp pain that worsens when taking a deep breath or coughing. Irritation of the diaphragm (the large muscle separating the chest and abdomen) can send pain signals up the phrenic nerve, leading to discomfort felt in the shoulder and scapular region.
Deeper Causes: Referred Pain from the Upper Abdomen
Internal organs situated in the upper left quadrant of the abdomen, below the diaphragm, are another source of referred pain to the left scapula. The spleen, which sits high on the left side, can cause pain in the left shoulder tip or shoulder blade if it ruptures or becomes severely enlarged. This specific pattern, known as Kehr’s sign, occurs because blood or fluid irritates the diaphragm, which then transmits the pain along the phrenic nerve.
The pancreas, located deep in the abdomen, can cause pain that radiates posteriorly toward the left shoulder blade during inflammation, such as acute pancreatitis. This pain is typically severe and often accompanied by intense upper abdominal pain that may wrap around the side. Severe stomach ulcers or gastric perforation can also irritate the underside of the diaphragm, leading to referred pain in the back.