Overview
Subacromial bursitis is inflammation of the bursa under the acromion, a bony part of the shoulder that helps reduce friction as the rotator cuff tendons glide. When the bursa becomes irritated, it can increase pain during shoulder movement, especially overhead or across the body. The pain can also make the shoulder feel stiff and weak because using it normally becomes uncomfortable. In many cases, symptoms improve with time and a well-planned nonsurgical approach.
Symptoms
People with subacromial bursitis often feel pain on the outer (lateral) side of the shoulder, which may worsen when lifting the arm, reaching overhead, or performing repetitive movements. Night pain is common, especially when lying on the affected shoulder. Some patients notice limited range of motion and difficulty reaching behind the back. The shoulder may feel tender to touch over the painful area.
Causes
Subacromial bursitis most often develops from repetitive overhead activity, sudden overuse, or mechanical irritation where tissues rub during arm elevation. It can also follow a minor injury or flare up in the setting of rotator cuff tendinopathy and shoulder impingement, where movement places extra stress on the bursa. Inflammatory processes can then amplify pain and swelling around the shoulder.
Risk Factors
Risk is higher in people who frequently work or exercise with overhead arm use, such as painting, lifting, swimming, or throwing. Age-related tendon wear and shoulder degeneration can contribute, even without a specific injury. Poor shoulder mechanics, limited mobility, and weakness in the rotator cuff or scapular stabilizers can also increase the likelihood of flare-ups. Smoking and uncontrolled diabetes may slow healing and increase persistent shoulder inflammation in some patients.
Prevention
To reduce recurrence, keep overhead activity within comfortable limits and gradually build strength and endurance rather than suddenly increasing volume. Maintain shoulder flexibility and use strengthening focused on the rotator cuff and scapular muscles to improve how the shoulder moves. Pay attention to technique during work and sports, and consider ergonomic adjustments to avoid sustained positions that provoke pain. If symptoms start, early modification of activity and guided physical therapy can help prevent a prolonged flare.
How the Diagnosis Is Evaluated
Clinicians typically diagnose subacromial bursitis based on a careful history of pain pattern and activities that trigger symptoms, along with a focused shoulder exam. Physical findings often include localized tenderness over the subacromial area and pain with specific shoulder movements, sometimes with partial motion limits due to pain. Imaging such as ultrasound or MRI may be used when symptoms are persistent or to rule out other causes like rotator cuff tears or calcific tendinitis. X-rays are sometimes obtained to check for arthritis or bone-related contributors, but they do not usually show bursal inflammation directly.
Nonsurgical Treatment Options
Initial treatment focuses on calming inflammation and restoring comfortable shoulder mechanics. Activity modification, relative rest from painful overhead motions, and short-term use of anti-inflammatory medications like NSAIDs (if safe for you) can reduce pain and swelling. Physical therapy is a cornerstone and usually includes gentle range-of-motion work, stretching, and progressive strengthening of the rotator cuff and scapular stabilizers to decrease irritation during arm elevation. Ice or heat may help symptom control, and clinicians may recommend a brief course of home exercises tailored to your movement limits. If pain persists, an ultrasound-guided corticosteroid injection into the subacromial space can provide targeted relief and help you participate in rehab more effectively. Some patients ask about biologic injections such as platelet-rich plasma; these may be considered by select clinicians, but evidence for subacromial bursitis is less consistent than for standard therapies.
When to Seek Medical Attention
Seek prompt medical attention if you have sudden severe shoulder pain after an injury, rapidly worsening swelling, or inability to lift the arm. Contact a clinician urgently if you develop fever, feel very ill, or have redness over the shoulder, because infection must be ruled out. Get evaluated sooner if you have progressive weakness, numbness or tingling down the arm, or symptoms that do not improve after several weeks of conservative care. Also seek care if night pain is worsening or you cannot perform basic daily activities due to shoulder limitations.
Frequently Asked Questions
It usually causes pain on the outer side of the shoulder that is worse with overhead reaching, sometimes with night pain and tenderness when you press the area.
Many people improve over a few weeks with activity changes and physical therapy, but some cases take longer, especially if the irritation keeps recurring.
Yes, for many patients a corticosteroid injection can reduce pain and inflammation enough to resume strengthening and restore function.
Next Steps
If your pain is triggered by overhead reaching or bothers you at night, consider booking an evaluation with a clinician or physical therapist to confirm the diagnosis and start a targeted rehab plan. In the meantime, avoid the specific activities that sharply worsen symptoms and use gentle, pain-limited motion to stay mobile. If symptoms worsen suddenly or you develop fever or marked weakness, seek medical care right away.