Left shoulder pain is usually caused by a muscle, tendon, or joint problem, but it can occasionally signal something more serious involving the heart, spleen, or nerves in the neck. Shoulder pain affects between 18% and 26% of adults, and the single most common cause is wear or irritation of the rotator cuff tendons, which accounts for up to 70% of all musculoskeletal shoulder pain. Understanding the pattern of your pain, when it started, and what other symptoms you have helps narrow the possibilities considerably.
When Left Shoulder Pain Is a Heart Warning
The reason most people search this question is concern about a heart attack, and that instinct is worth taking seriously. Heart attacks can cause pain or discomfort that radiates into one or both arms, the back, neck, jaw, or stomach. The chest discomfort itself typically feels like pressure, squeezing, or fullness in the center of the chest. It lasts more than a few minutes, or it comes and goes.
Shoulder pain alone, without any other symptoms, is unlikely to be cardiac. The red flags that push left shoulder pain into emergency territory are shortness of breath (with or without chest discomfort), breaking out in a cold sweat, nausea, and lightheadedness. If you’re experiencing shoulder pain alongside any combination of those symptoms, call emergency services. The distinction matters because cardiac shoulder pain almost always arrives with company, while musculoskeletal shoulder pain tends to stand on its own.
Rotator Cuff Injuries
The rotator cuff is a group of four tendons that hold your shoulder joint in place and let you lift and rotate your arm. When one or more of these tendons becomes irritated, partially torn, or fully torn, you typically feel a dull ache deep in the shoulder that gets worse at night. Many people first notice the problem when they have trouble reaching behind their back to tuck in a shirt or lifting their arm to comb their hair.
Rotator cuff pain often disrupts sleep because lying on the affected side compresses the inflamed tissue. Arm weakness is another hallmark. Some rotator cuff injuries, though, cause no pain at all and are only discovered incidentally on imaging. The severity ranges from mild tendon irritation that responds to rest and physical therapy to complete tears that may need surgical repair. Your doctor can perform simple in-office maneuvers (pressing down on your outstretched arm in specific positions, rotating your shoulder while watching for pain) to get a good initial read on whether the rotator cuff is involved.
Frozen Shoulder
Frozen shoulder, or adhesive capsulitis, is a condition where the tissue surrounding the shoulder joint gradually tightens and forms scar-like bands, severely limiting your range of motion. It progresses through distinct stages over a long timeline. The “freezing” stage lasts roughly 3 to 9 months, during which pain increases and movement becomes more restricted. The “frozen” stage, from about 9 to 15 months, brings less pain but the stiffness plateaus at its worst. Finally, the “thawing” stage runs from 15 to 24 months, during which motion slowly returns.
Frozen shoulder is more common in people with diabetes and in those who’ve had their arm immobilized after surgery or injury. The left shoulder is affected just as often as the right. The total course can stretch to two years, which is why early physical therapy matters for maintaining as much mobility as possible throughout.
Pinched Nerve in the Neck
A compressed nerve root in the cervical spine (the neck portion of your backbone) can send pain, tingling, numbness, or weakness into the shoulder, arm, chest, or upper back. This is called cervical radiculopathy. The nerves that exit between the vertebrae in your neck branch directly into your shoulders and arms, so a problem in the neck can feel like a shoulder problem.
The telltale sign that your shoulder pain is actually coming from your neck is the presence of nerve-type symptoms: pins and needles, numbness running down the arm, or a feeling of weakness when gripping objects. Turning or tilting your head may change the intensity of the pain. This is different from a rotator cuff issue, where the pain is localized in the shoulder itself and worsens mainly with arm movement.
Referred Pain From the Spleen
The left shoulder specifically (not the right) can be a referral site for problems below the diaphragm, particularly a ruptured or injured spleen. This is known as Kehr’s sign. It happens because bleeding from the spleen irritates the left phrenic nerve, which runs from the neck down through the left side of the chest. The pain tends to be worse when you breathe in.
This type of referred pain is most relevant if you’ve recently experienced abdominal trauma, such as a car accident, a fall, or a sports collision. Splenic injury is uncommon without some triggering event, so isolated left shoulder pain without a history of trauma is unlikely to involve the spleen. But if you have left shoulder pain that appeared after an abdominal blow, especially with tenderness in the upper left abdomen, it warrants urgent evaluation.
A Rare but Important Cause: Lung Tumors
A Pancoast tumor is a type of lung cancer that grows at the very top of the lung, near the shoulder. Because of its location, it can press on the brachial plexus, the bundle of nerves running from the upper chest into the neck and arms. This causes severe, persistent shoulder pain that may radiate down the arm toward the wrist and pinky finger, along with arm and hand weakness.
This is rare, and it’s listed here not to cause alarm but because it’s the kind of cause that gets missed when people assume shoulder pain is always muscular. The distinguishing features are pain that doesn’t respond to typical treatments, doesn’t follow the pattern of a rotator cuff injury, and worsens progressively over weeks. A history of smoking raises the concern further.
How Shoulder Pain Is Evaluated
A physical exam can reveal a surprising amount. During a shoulder evaluation, a clinician will ask you to move your arm in specific directions while they apply resistance or guide the motion. For instance, holding your arms out in front of you with thumbs pointing down while someone pushes downward tests the supraspinatus, one of the rotator cuff tendons. Other maneuvers involve flexing the arm overhead or internally rotating it to check for impingement, where tendons get pinched between bones during movement.
If the exam points toward soft tissue damage, imaging (usually an MRI or ultrasound) confirms the extent. If nerve involvement is suspected, your doctor may order imaging of the cervical spine or nerve conduction studies. For cardiac concerns, an electrocardiogram and blood tests can quickly rule a heart problem in or out.
What Treatment Typically Looks Like
For the most common causes, rotator cuff issues and impingement, the first line of treatment is physical therapy focused on strengthening the muscles around the shoulder and improving mobility. Many people see meaningful improvement within 6 to 12 weeks of consistent exercise.
When pain is too intense to allow productive physical therapy, a cortisone injection into the shoulder joint can provide a window of relief. These injections typically last 3 to 6 months, sometimes longer, and work by reducing the inflammation driving the pain. They’re not a permanent fix, but they can make it possible to participate in rehabilitation that addresses the underlying problem. For complete rotator cuff tears or frozen shoulder that doesn’t respond to conservative treatment, surgical options exist, though most people try several months of non-surgical treatment first.
For nerve-related shoulder pain originating in the neck, treatment focuses on the cervical spine: physical therapy, posture correction, and sometimes epidural injections. The approach depends on whether the compression is from a herniated disc, bone spur, or degenerative narrowing of the spinal canal.