Back pain that is localized to the upper left side can be both frustrating and puzzling, especially when the cause is unknown. Depending on your health history, you may wonder if the pain is related to your spine, shoulder, ribs, or possibly an internal organ, such as the heart. Let’s look at some possible causes of upper left back pain, and when it requires a doctor visit.

Sometimes the cause of upper back pain is easy to find. And other times, it's more mysterious. Watch: Causes of Upper Back Pain Video

Muscle strain

Upper back pain is commonly related to a muscle strain, which can feel anywhere from a dull ache to an intense or burning pain. For people experiencing mild to moderate upper left back pain with recent onset, muscle strain is by far the most common cause. Some potential muscle strain causes include:

  • Overuse. When performing repetitive motions, such as painting or rowing, muscles in the shoulders and upper back may become overused and strained. Lifting an item that is too heavy can also strain an upper back muscle.
  • Poor posture. Sitting hunched forward or to one side can stress the spine and muscles. Sitting with poor posture for long periods of time or on a regular basis can eventually lead to muscle strain, which may be felt on one side more than the other.

    See Good Posture Helps Reduce Back Pain

  • Collision. A high-impact collision, such as during a football or hockey game, can cause a muscle injury and pain.

Sometimes an intercostal muscle, which is a small muscle between adjacent ribs, can be strained in the upper back and lead to pain and possibly difficulty breathing.

See Upper Back Pain from Intercostal Muscle Strain

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Foraminal stenosis

On each side of the vertebra is a bony opening called the intervertebral foramen where the spinal nerve exits the spinal canal. When this foramen narrows, such as due to facet joint osteoarthritis, bone spurs, and/or a herniated disc, it is called foraminal stenosis. When there is less space in the foramen, the spinal nerve can become pinched or inflamed.

Cervical foraminal stenosis in the lower neck may radiate pain down into the shoulder blade region. While less common, thoracic foraminal stenosis may also cause pain in the upper back to one side, such as the left side. Radicular pain from foraminal stenosis can range from mild to burning or electric-like, and sometimes it’s accompanied by tingling, numbness, and/or weakness.

Read more about Cervical Foraminal Stenosis

Vertebral compression fracture

When small cracks in a vertebra result in at least 15% of its height being lost, it’s considered a vertebral compression fracture. The thoracic spine (middle and upper back) is where vertebral compression fractures typically occur. People with osteoporosis, a condition where the bones become weakened, are most likely to have compression fractures, which can occur without any type of high-impact collision or fall. It is also possible for vertebral compression fractures to occur during heavy lifting, sports, auto or bike accidents, or falls.

Watch Spinal Compression Fracture Video

Most spinal compression fractures are felt in the middle or on both sides of the spine equally. However, in some cases the pain can be felt more on one side than the other. Some compression fractures are more severe and could involve a spinal nerve becoming compressed. So if the spinal nerve on the left side became pinched or inflamed, the pain may be felt more toward the left.

See Vertebral Fracture Symptoms

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Internal organ problem

While rare, sometimes a problem with an internal organ can manifest primarily as upper left back pain. A couple examples include:

  • Heart attack. Most heart attacks involve chest pain, but not always. It is possible for heart attack symptoms to be felt as more of a one-sided pain in the arm, shoulder, and/or upper back. These symptoms may occur more commonly on the left side, but they can also occur on the right side or both sides. Other potential symptoms could include weakness, light-headedness, trouble breathing, or pain in the jaw or neck.
  • Lung cancer. While the initial symptoms of lung cancer typically involve coughing, hoarseness, or chest pain, it is possible for back pain to be the first noticeable symptom. For example, a tumor in the left lung may grow into the nearby spine or ribs, which could cause upper left back pain.

Various other causes may also lead to upper left back pain.

When to see a doctor

When upper left back pain persists for a couple weeks, it’s important to visit a doctor in order to get an accurate diagnosis and pain relief. If upper back left pain is ever accompanied by numbness, weakness, severe headache, nausea, trouble walking, bowel/bladder incontinence, or other troubling symptoms, seek immediate medical attention.

See When Back Pain May Be a Medical Emergency

Learn more

Causes of Upper Back Pain

Early Treatments for Upper Back Pain

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