Left shoulder pain most often comes from a musculoskeletal problem like a strained rotator cuff, inflamed bursa, or pinched nerve in the neck. But it can also be a warning sign of something more serious, including a heart attack or an injury to an internal organ like the spleen. The location alone doesn’t tell you the cause. What matters is how the pain started, what makes it worse, and whether you have other symptoms alongside it.
When Left Shoulder Pain Signals a Heart Attack
This is the concern that drives most people to search this topic, so let’s address it first. Heart attacks most commonly cause discomfort in the center of the chest, described as pressure, squeezing, or fullness that lasts more than a few minutes or comes and goes. But the pain frequently radiates to one or both arms, the back, neck, jaw, or stomach. Left shoulder pain on its own, without any other symptoms, is unlikely to be cardiac.
The combination of symptoms matters. If your left shoulder pain comes with shortness of breath, a cold sweat, nausea, lightheadedness, or chest pressure, call 911 immediately. Women are more likely than men to experience these “atypical” symptoms without obvious chest pain, which makes them easier to dismiss.
Rotator Cuff Problems
The rotator cuff is a group of tendons that hold your shoulder joint together and let you lift and rotate your arm. These tendons break down over time, especially with repetitive overhead motions, and when the breakdown outpaces the body’s ability to repair, small tears develop and cause inflammation. This is tendonitis, the most common cause of shoulder pain in adults.
Tendonitis builds gradually. You’ll notice a dull ache that worsens when reaching overhead, behind your back, or out to the side. Sleeping on the affected shoulder often makes it worse. If the tendon damage progresses, it can result in a partial or full rotator cuff tear. Acute tears also happen suddenly from a fall, a hard pull, or a shoulder dislocation, and they cause an immediate inability to raise or rotate the arm.
Physical therapy improves outcomes for both partial tears and small to medium full-thickness tears, with strong evidence behind it. A 2025 guideline from the American Academy of Orthopaedic Surgeons confirms that both physical therapy and surgery produce significant improvement for small to medium tears, meaning surgery isn’t always necessary. For low-grade partial tears, physical therapy is the recommended first step, with surgery reserved for people who still have pain and limited function after a full course of rehab. A single corticosteroid injection can help with short-term pain relief while you work through physical therapy, though it’s not a long-term fix.
Shoulder Bursitis
A fluid-filled sac called a bursa sits between your rotator cuff tendons and the bone above them, cushioning the joint during movement. When this bursa becomes irritated and swollen, the result is bursitis. It feels similar to tendonitis and often occurs alongside it.
The hallmark of shoulder bursitis is pain that can come on suddenly or build up over days. You may feel a constant dull ache, but the pain turns sharp or pinching when you lift your arm overhead. Stiffness, warmth over the joint, and tenderness even to light touch are common. Lying on the affected shoulder at night typically makes the pain noticeably worse.
Pinched Nerve in the Neck
A pinched nerve in the cervical spine (your neck) can send pain radiating down into your shoulder, arm, chest, or upper back. This is called cervical radiculopathy, and it happens when a herniated disc, bone spur, or narrowed spinal canal compresses a nerve root. The pain often follows a specific path from the neck into the shoulder and down the arm, and it may come with numbness, tingling, or muscle weakness in the arm or hand.
The key difference from a shoulder-joint problem is that moving your neck, not your shoulder, tends to trigger or worsen the pain. Turning your head, looking up, or tilting to one side may reproduce the symptoms. If your shoulder pain comes with weakness in your grip or a pins-and-needles sensation running down your arm, a neck issue is a strong possibility.
Frozen Shoulder
Frozen shoulder is a condition where the tissue surrounding the joint thickens and tightens, gradually restricting movement until the shoulder is nearly immobile. It progresses through three distinct stages. The “freezing” stage lasts six weeks to nine months, during which stiffness increases and pain slowly worsens, often disrupting sleep. The “frozen” stage lasts two to six months, where pain may ease but the shoulder remains very stiff and daily tasks become difficult. Finally, the “thawing” stage brings a slow return of movement and can take six months to two years.
The entire process from onset to full recovery typically spans one to three years. Frozen shoulder is more common in people with diabetes, thyroid disorders, or after a period of immobilization following surgery or injury.
Referred Pain From Internal Organs
Sometimes the source of left shoulder pain isn’t in the shoulder at all. Your brain can misinterpret pain signals from internal organs as coming from the shoulder because the nerves share overlapping pathways in the spinal cord.
A ruptured spleen is one of the more important examples. After a rupture, bleeding irritates the left phrenic nerve, which runs from the neck through the left side of the chest. This causes pain that seems to move to the left shoulder or left side of the chest, a phenomenon called Kehr’s sign. A ruptured spleen typically follows abdominal trauma, like a car accident or a blow during contact sports, and comes with severe abdominal pain, tenderness on the left side, and sometimes dizziness from blood loss.
Other conditions that can refer pain to the shoulder area include lung problems, pancreatitis, and liver issues. If your left shoulder pain appeared without any injury and comes with abdominal pain, difficulty breathing, or feeling faint, it’s worth getting evaluated promptly.
Parsonage-Turner Syndrome
This is a rare but underrecognized cause of sudden, severe shoulder pain. It involves inflammation of the network of nerves that supply the shoulder and arm, and it strikes without an obvious trigger. The pain is typically described as sharp or stabbing, often worse at night, followed within days or weeks by noticeable weakness and muscle wasting in the shoulder, arm, or hand.
A visible “winging” of the shoulder blade, where it sticks out prominently from the back, occurs in 30% to 70% of cases. Because the symptoms can mimic a rotator cuff tear or cervical disc problem, many people undergo unnecessary surgeries before getting the correct diagnosis. MRI, nerve ultrasound, and electrodiagnostic testing help distinguish it from other conditions.
How to Tell What’s Causing Your Pain
A few patterns can help you narrow down the likely source:
- Pain with overhead reaching or rotation: Rotator cuff tendonitis, bursitis, or impingement. Worse at night when lying on that side.
- Pain that radiates from neck to shoulder and down the arm: Pinched nerve in the cervical spine, especially if accompanied by tingling or weakness.
- Gradual loss of all shoulder movement: Frozen shoulder, particularly if it’s been worsening over weeks to months.
- Sudden inability to lift the arm after an injury: Acute rotator cuff tear.
- Shoulder pain with chest pressure, shortness of breath, or sweating: Possible cardiac event. Call 911.
- Shoulder pain with abdominal pain and no shoulder injury: Possible referred pain from an organ like the spleen or pancreas.
During a physical examination, a clinician will typically test for impingement by positioning your arm in specific ways that compress the structures inside the joint. Pain during these movements points toward bursitis, tendonitis, or a tear. Imaging with X-ray, ultrasound, or MRI helps confirm the diagnosis when the physical exam isn’t definitive.