The most common cause of shoulder pain when lifting your arm is impingement, where soft tissues get pinched inside your shoulder joint during overhead movement. Experts estimate impingement accounts for roughly half of all shoulder pain cases. But several other conditions can produce the same symptom, and understanding the differences helps you figure out what you’re dealing with and what to do about it.
What Happens Inside Your Shoulder
Your shoulder has a narrow gap between the top of your upper arm bone and the bony roof of your shoulder blade. This gap, called the subacromial space, is normally only 1.0 to 1.5 centimeters wide. When you raise your arm out to the side, reach forward, or rotate your shoulder inward, that space gets even smaller as the top of your arm bone migrates upward toward your shoulder blade.
If anything in that tight space is swollen, thickened, or out of position, raising your arm compresses those structures and triggers pain. The tissues most commonly caught in this squeeze are the tendons of your rotator cuff (the group of four tendons that stabilize and move your shoulder joint) and a small fluid-filled cushion called a bursa that sits between those tendons and the bone above them.
A hallmark pattern of this type of pain is the “painful arc,” where your shoulder feels fine at the beginning and end of the motion but hurts specifically between about 60 and 120 degrees of elevation. If that matches your experience, impingement is a strong possibility.
Shoulder Impingement and Its Subtypes
Shoulder impingement is really an umbrella term. Your provider may narrow it down to one of a few specific problems:
- Rotator cuff tendinitis: The tendons that move your shoulder become irritated and inflamed, usually from repetitive overhead activity. This is the most common subtype.
- Shoulder bursitis: The bursa cushioning your rotator cuff swells up, taking up space in an already tight area and increasing the pinching effect.
- Bone spur or acromion shape: The bony roof of your shoulder blade is supposed to be relatively flat. Some people are born with a more curved or hooked shape, and others develop bony growths (spurs) with age. Either variation narrows the space and makes impingement more likely.
These subtypes often overlap. Tendinitis can cause swelling that irritates the bursa, and a hooked acromion can accelerate wear on the tendons. The resulting pain typically worsens when you extend your arm overhead, lower it back down, or reach for something.
Rotator Cuff Tears
When tendinitis goes on long enough, the tendon’s ability to repair itself falls behind the rate of damage. Micro-tears develop, and over time those can progress into a partial or complete rotator cuff tear. The key difference between tendinitis and a tear is strength loss. With tendinitis, raising your arm hurts but you can still do it. With a significant tear, you may find it genuinely difficult or impossible to lift or rotate your arm, not just painful.
Tears can also happen suddenly. A fall, a shoulder dislocation, or a single forceful movement can overwhelm the tendon all at once. An acute tear like this typically causes immediate inability to raise your arm, along with sharp pain. If you experienced a sudden injury and now can’t lift your arm at all, that’s a different situation than gradual pain that’s been building over weeks or months.
Biceps Tendinitis
Your biceps muscle connects to your shoulder blade via a long tendon that runs through the front of your shoulder joint. When this tendon becomes inflamed, it produces pain or tenderness at the front of the shoulder that gets worse with overhead lifting or continued physical activity. Biceps tendinitis often develops alongside rotator cuff problems since the two structures share close quarters. If your pain is concentrated in the front of the shoulder rather than on top or along the side, this tendon may be involved.
Frozen Shoulder
Frozen shoulder (adhesive capsulitis) is a distinct condition where the capsule surrounding your shoulder joint thickens and tightens. It doesn’t just hurt when you lift your arm; it progressively restricts how far your arm can move in every direction. The condition moves through three phases. The freezing phase brings worsening pain, especially at night, as stiffness sets in over 2 to 9 months. The frozen phase shifts the main problem from pain to stiffness, lasting another 4 to 12 months. Finally, a thawing phase gradually restores movement. The entire process can take anywhere from several months to 2 or 3 years.
Frozen shoulder is worth considering if your range of motion is shrinking over time and your shoulder feels stiff even when someone else tries to move it for you. It’s more common in people with diabetes and tends to appear between ages 40 and 60.
How These Conditions Are Identified
A physical exam is usually the starting point. Your provider will move your arm into specific positions to see which motions reproduce your pain. Two commonly used maneuvers for impingement involve your provider raising your arm in particular ways to compress the subacromial space. These tests are reasonably good at detecting impingement (catching about 79% of true cases) but less precise at ruling it out, which is why imaging like an MRI or ultrasound is sometimes needed, particularly if a tear is suspected.
The painful arc test, where you slowly raise your arm out to the side, is another useful indicator. Pain that kicks in around 60 degrees and fades after 120 degrees points strongly toward a rotator cuff or bursa issue rather than a joint capsule or bone problem.
Physical Therapy as First-Line Treatment
For impingement and rotator cuff tendinitis, physical therapy is the standard starting point, and the evidence strongly supports it. A systematic review comparing surgery plus physical therapy to physical therapy alone found no clinically meaningful difference in pain or function at 3 months, 6 months, or even 5 and 10 years out. In other words, adding surgery to a rehab program didn’t produce better results than rehab on its own for most people with impingement.
The typical approach focuses on strengthening the muscles that pull your arm bone downward and back during overhead movement, creating more space in the subacromial gap. Stretching and posture work often play a role too, especially if rounded shoulders or a stiff upper back are contributing to the problem. According to specialists at the Hospital for Special Surgery, daily targeted exercises can produce noticeable pain improvement within about two weeks. If you’ve been consistent for six weeks without improvement, or your pain is getting worse or disrupting your sleep, that’s a reasonable point to escalate care with a physical therapist or shoulder specialist.
Less Common but Serious Causes
Most shoulder pain when lifting your arm comes from the mechanical causes described above. Occasionally, though, shoulder pain has a non-orthopedic source. A heart attack can produce shoulder pain, typically on the left side, often accompanied by chest pressure, shortness of breath, or pain radiating down the arm. Gallbladder problems and certain abdominal conditions can also refer pain to the shoulder area, particularly the right shoulder, because of shared nerve pathways involving the diaphragm.
These causes are uncommon, but if your shoulder pain came on suddenly without any physical trigger, feels different from a muscle or joint issue, or is accompanied by chest tightness, nausea, or abdominal symptoms, those are signs that something beyond the shoulder itself may be involved.