Shoulder bursitis is inflammation of a small, fluid-filled sac called the subacromial bursa that sits between the bony roof of your shoulder and the rotator cuff muscles beneath it. This bursa normally acts as a cushion, reducing friction every time you raise your arm. When it becomes swollen and irritated, the space it occupies shrinks, and movements that were once painless start to hurt, especially reaching overhead or out to the side.
What the Subacromial Bursa Does
Your shoulder joint has more range of motion than any other joint in your body, and that freedom comes with a cost: the soft tissues inside are constantly sliding past each other. The subacromial bursa is a thin, slippery sac positioned between the acromion (the bony point at the top of your shoulder) and the supraspinatus, one of the four rotator cuff muscles. Its job is to protect that muscle from grinding against bone every time you lift your arm. When the bursa is healthy, you never notice it. When it’s inflamed, it swells and thickens, taking up space in an already tight corridor. That’s when pain begins.
What Causes It
Repetitive overhead motion is the single most common trigger. Painters, carpenters, plumbers, landscapers, and warehouse workers develop shoulder bursitis at higher rates than the general population because their daily tasks involve sustained or forceful arm movements. Sports that rely on throwing, rowing, or swinging a racket, bat, or club carry the same risk.
You don’t need to be an athlete or a tradesperson to develop it, though. Any activity that repeatedly forces your arm above shoulder height can irritate the bursa over time. Gardening, playing a musical instrument, or even reorganizing high shelves during a move can set it off. A single traumatic blow to the shoulder, like a fall, can also cause sudden inflammation. Less commonly, bacterial infections from elsewhere in the body spread to the bursa, causing a form called infectious (or septic) bursitis that requires different treatment. Inflammatory conditions like rheumatoid arthritis and gout also increase your risk.
How Shoulder Bursitis Feels
The hallmark symptom is pain on the outside of the shoulder that worsens when you raise your arm, especially in the arc between about 60 and 120 degrees. This range is sometimes called the “painful arc” because it’s the point where the swollen bursa gets pinched between the acromion and the rotator cuff. Reaching behind your back, like tucking in a shirt or fastening a bra, often hurts as well.
Nighttime pain is extremely common. Lying on the affected shoulder compresses the already irritated bursa, and many people find themselves waking up or unable to fall asleep on that side. You may also notice warmth or mild swelling at the top of the shoulder, though visible swelling is less dramatic than bursitis in other joints like the knee or elbow. Over time, the pain can make you move your shoulder less, which leads to stiffness and weakness that compound the original problem.
How It’s Diagnosed
Diagnosis usually starts with a physical exam. Your doctor will move your arm through different positions to see which ones reproduce your pain. Two common tests are the Neer test and the Hawkins-Kennedy test. In the Neer test, the examiner lifts your straightened arm forward and overhead while your forearm is turned inward. This narrows the subacromial space and squeezes the bursa. If pain flares, the test is considered positive. For the Hawkins-Kennedy test, your arm is raised to 90 degrees and the examiner rotates it inward while bringing it across your body. Pain during this maneuver points to impingement of the bursa.
These physical tests can identify impingement, but they can’t always distinguish bursitis from a rotator cuff tear, since both conditions share the same tight space and produce overlapping symptoms. If a tear is suspected, particularly if you also have notable weakness, an MRI is typically ordered. MRI can detect even small partial tears and can show whether the bursa itself is significantly thickened or if there’s fluid accumulation.
How Bursitis Differs From a Rotator Cuff Tear
Bursitis and rotator cuff injuries often coexist and feel similar, which makes it easy to confuse them. Both cause pain with overhead reaching, and both can wake you at night. The key difference is strength. With isolated bursitis, your rotator cuff muscles are intact, so once you push past the painful arc you can usually complete the motion with normal power. A rotator cuff tear, on the other hand, causes measurable weakness: you may struggle to hold your arm up against light resistance, or your arm may drop when the examiner releases it.
Chronic bursitis can also set the stage for a tear. Prolonged inflammation in the subacromial space creates friction that gradually weakens the rotator cuff tendons. Over time, that weakening can progress from tendinitis to a partial tear to a complete tear. Treating bursitis early helps break this cycle.
Treatment Without Surgery
Most cases of shoulder bursitis resolve without surgery. The first step is rest from the activity that triggered the inflammation, combined with icing the shoulder two or three times a day for 20 to 30 minutes each session. Over-the-counter anti-inflammatory medications like ibuprofen or naproxen help reduce both pain and swelling. Expect to use these strategies for several weeks before the swelling fully subsides.
Physical therapy is one of the most effective treatments for preventing recurrence. Early-stage rehab focuses on gentle range-of-motion exercises. A simple starting exercise is the posterior shoulder stretch: hold the elbow of your affected arm with your opposite hand and gently pull the arm across your body until you feel a stretch across the back of the shoulder. Hold for 15 to 30 seconds, repeat two to four times, and do this daily. As pain decreases, therapy progresses to strengthening exercises that stabilize the rotator cuff and the muscles around the shoulder blade. Stronger muscles keep the humeral head (the ball of your upper arm bone) centered in the joint, which opens up the subacromial space and takes pressure off the bursa.
If several weeks of rest, medication, and therapy don’t bring adequate relief, a corticosteroid injection into the subacromial space is the next option. These injections work quickly: over 95% of patients in one study reported reduced pain and improved function within six weeks. Pain relief tends to be most noticeable at the four-to-six-week mark, though the benefit can start fading by eight to twelve weeks. In many cases, one injection is enough to break the pain cycle and allow physical therapy to take over. Some people need a second injection, but repeated steroid shots carry a risk of weakening nearby tendons, so doctors typically limit the number given in a single year.
When Surgery Becomes an Option
Surgery is reserved for cases that don’t respond to months of conservative treatment. The most common procedure is arthroscopic subacromial decompression, in which a surgeon uses small instruments inserted through tiny incisions to shave away part of the acromion bone and remove the inflamed bursa tissue. This widens the subacromial space so the rotator cuff and bursa no longer get pinched during arm movement. Recovery involves several weeks in a sling followed by a structured physical therapy program, and most people return to full activity within three to six months.
What You Can Do to Prevent Flare-Ups
If your work or sport requires overhead movement, building and maintaining rotator cuff and shoulder blade strength is the most reliable way to protect your bursa long-term. Warm up before repetitive tasks, and take breaks when you can. Varying your movement patterns throughout the day, rather than doing one motion for hours, reduces cumulative stress on the bursa. If you’ve had bursitis once, continuing a simple home exercise program even after the pain resolves significantly lowers the chance of it coming back.