Subacromial bursitis is inflammation of a small, fluid-filled sac (called a bursa) that sits between the top of your shoulder blade and your rotator cuff tendons. This bursa normally acts as a cushion, reducing friction when you move your arm. When it becomes irritated or swollen, the result is shoulder pain that can range from a mild ache to sharp discomfort with everyday movements like reaching overhead or sleeping on the affected side.
Where the Subacromial Bursa Sits
Your shoulder is one of the most mobile joints in your body, and that mobility comes with a lot of moving parts rubbing against each other. The subacromial bursa sits in a tight space between the bony roof of your shoulder (the acromion) and the rotator cuff muscle underneath. Its job is to protect that rotator cuff muscle from being worn down by repeated contact with the bone above it. Think of it as a biological shock absorber: a thin, slippery pad that lets tendons and bones glide past each other smoothly.
When the bursa is healthy, you never notice it. It contains just a small amount of lubricating fluid. But when it’s irritated, the lining thickens and produces excess fluid, swelling inside a space that’s already quite narrow. That swelling is what causes pain, because every time you move your arm, inflamed tissue gets compressed between bone and tendon.
What Causes It
The most common trigger is repetitive overhead activity. Painters, swimmers, tennis players, and anyone whose work or sport involves raising the arm above shoulder height repeatedly are at higher risk. Each time the arm goes up, the space between the acromion and the rotator cuff narrows, pinching the bursa. Over time, this repeated compression irritates the bursa and triggers inflammation.
A single traumatic event can also set it off. Falling onto an outstretched hand, landing on the shoulder, or a direct blow can cause sudden swelling. In some people, the shape of the acromion itself contributes. A downward-curving or hooked acromion leaves less room in the subacromial space, making the bursa more vulnerable to compression even during normal movement. Age-related bone spurs on the underside of the acromion can have the same effect.
Subacromial bursitis frequently overlaps with a broader condition called shoulder impingement syndrome, where the rotator cuff tendons and the bursa are both being pinched. It can also coexist with rotator cuff tendinopathy, making it tricky to isolate as the sole source of pain.
How It Feels
The hallmark symptom is pain on the outside and top of the shoulder, particularly when you lift your arm out to the side or overhead. Many people notice a “painful arc,” where the shoulder feels fine at rest and fine once the arm is fully raised, but hurts in the middle range of movement (roughly 60 to 120 degrees of elevation). That’s the range where the bursa gets squeezed the most.
Night pain is common and often what drives people to seek help. Lying on the affected shoulder compresses the already swollen bursa, and many people find themselves waking up or unable to fall asleep on that side. Reaching behind your back (like tucking in a shirt or fastening a bra) can also provoke a sharp catch of pain. Over time, if the inflammation persists, you may start losing range of motion simply because you stop using the shoulder through its full arc to avoid discomfort.
How It’s Diagnosed
Diagnosis typically starts with a physical exam. Two clinical tests are used most often. In the Hawkins test, the examiner bends your arm to 90 degrees in front of you and then rotates it inward. If this reproduces your pain, it suggests something in the subacromial space is being pinched. In the Neer sign, the examiner lifts your arm forward and upward while stabilizing your shoulder blade. Pain during this motion points toward subacromial impingement.
Neither test alone is definitive because several shoulder conditions can produce similar pain. If the picture is unclear, imaging helps. An X-ray can reveal bone spurs or the shape of the acromion. Ultrasound or MRI can show fluid buildup in the bursa, thickening of the bursal lining, and whether the rotator cuff tendons themselves are damaged. A diagnostic injection of a numbing agent into the subacromial space is sometimes used: if the injection temporarily eliminates your pain, it confirms that the subacromial space is the source.
First-Line Treatment
Most cases of subacromial bursitis resolve without surgery. The initial approach centers on reducing inflammation while gradually restoring normal movement. That means temporarily avoiding the specific overhead activities or motions that provoke your pain. Complete immobilization isn’t recommended because it can lead to stiffness, but modifying how you use the shoulder, especially cutting out repetitive overhead reaching, gives the bursa a chance to calm down.
Over-the-counter anti-inflammatory medications like ibuprofen or naproxen help reduce both pain and swelling. Ice applied for 15 to 20 minutes several times a day can also ease acute flare-ups. These steps alone are often enough for mild cases caught early.
Corticosteroid Injections
When oral anti-inflammatories and rest aren’t enough, a corticosteroid injection into the subacromial space is a common next step. In a study of 100 patients with rotator cuff problems (about half of whom had confirmed subacromial bursitis), ultrasound-guided corticosteroid injections led to significant improvement in 60% of patients at three months. Interestingly, the presence of bursitis itself didn’t predict who would respond better or worse to the injection, likely because bursitis rarely exists in isolation from tendon irritation.
The injection typically provides relief within a few days. Some people experience a temporary increase in pain for 24 to 48 hours before the steroid kicks in. Repeated injections are generally limited to two or three per year because corticosteroids can weaken tendons over time.
Physical Therapy and Rehabilitation
Physical therapy is the cornerstone of lasting recovery. A typical conditioning program runs 4 to 6 weeks and follows a logical progression: first restore range of motion, then rebuild strength, then return to full activity. The American Academy of Orthopaedic Surgeons recommends starting each session with 5 to 10 minutes of light cardio (walking, stationary cycling) followed by stretching before moving to strengthening work.
Early exercises focus on gentle, pain-free movement. Pendulum swings (leaning forward and letting the arm hang and swing in small circles) help maintain mobility without loading the joint. Passive stretches for internal and external rotation restore flexibility in the rotator cuff. The sleeper stretch, performed lying on the affected side with the arm bent in front of you and gently pressed downward, targets internal rotation stiffness that’s common with bursitis.
As pain decreases, strengthening exercises are added. Standing rows, external and internal rotation with a resistance band, scapular retraction exercises, and trapezius strengthening all help stabilize the shoulder blade and take pressure off the subacromial space. Bent-over horizontal abduction and rotation exercises with light weights build endurance in the muscles that control how the shoulder blade moves during overhead reaching. Once you’ve recovered, performing these exercises 2 to 3 days a week serves as ongoing maintenance to prevent recurrence.
When Surgery Is Considered
Surgery is reserved for cases that don’t respond to conservative treatment. Multiple randomized clinical trials have found no benefit to surgery as a first-line approach for subacromial bursitis. The procedure, called arthroscopic subacromial decompression, involves removing inflamed bursal tissue and shaving away any bone spurs or overhang from the acromion to create more room. It’s performed through small incisions with a camera, so recovery is faster than open surgery, but it’s only indicated after months of physical therapy, injections, and activity modification have failed to provide adequate relief.
Recovery Timeline
Mild cases that are caught early and managed with rest, anti-inflammatories, and activity changes often improve within a few weeks. Moderate cases that require physical therapy typically see meaningful improvement over 4 to 6 weeks of consistent exercise, though full resolution can take 2 to 3 months. Chronic bursitis, especially when it coexists with rotator cuff damage or structural impingement, can take longer and may require corticosteroid injections or, in stubborn cases, surgery to fully resolve.
The biggest factor in recovery speed is how quickly you address it. Continuing to push through overhead activities while the bursa is inflamed tends to turn a short-lived problem into a chronic one. Early modification of the aggravating activity, combined with targeted rehabilitation, gives most people the best shot at a complete and lasting recovery.