Swollen Shoulder: Causes, Location Clues and When to Worry

What a swollen shoulder looks and feels like

The shoulder is less obviously swollen than a knee or ankle because a thick layer of muscle (the deltoid) covers it. When swelling is visible, it usually means a fair amount of fluid, blood or tissue has built up. Compare both shoulders in a mirror: the swollen one looks fuller, rounder or higher, and the bony points may be harder to see.

Where the swelling sits gives the best clue to its cause:

Common causes of shoulder swelling

Injuries

• AC joint separation: a fall onto the point of the shoulder tears the ligaments joining the collarbone to the shoulder blade. The result is swelling and a step or bump at the top of the shoulder. See AC joint separation.
• Fracture: a broken collarbone, upper arm bone (humerus) or shoulder blade causes rapid swelling and bruising that often tracks down the arm over 2 to 3 days. Older adults with osteoporosis can break the upper humerus in a simple fall.
• Dislocation: the ball pops out of the socket, usually forward. The shoulder looks squared off rather than rounded, and the arm is held away from the body. See dislocated shoulder.
• Muscle strain or bruise: a strained deltoid, trapezius or rotator cuff muscle can swell and feel tender after heavy lifting or a direct blow. A large bruise can collect into a firm, tender lump called a hematoma.
• Rotator cuff tear: an acute tear after a fall or lift may cause swelling, weakness lifting the arm and night pain.

Bursitis

A bursa is a small fluid-filled cushion that lets tendons glide over bone. The subacromial bursa sits under the top of the shoulder. Repetitive overhead work, impingement or a fall can inflame it, causing pain on lifting the arm, tenderness on the outer shoulder and sometimes soft swelling. Bursitis can also be caused by infection or gout, which makes the area hot and red.

Arthritis and crystal disease

• Osteoarthritis of the glenohumeral or AC joint causes stiffness, grinding and occasional swelling. It is most common after age 50 and after old injuries.
• Rheumatoid arthritis and other inflammatory types cause swelling in both shoulders along with the hands, wrists or feet, plus morning stiffness lasting more than 30 minutes.
• Gout and pseudogout: crystals in the joint trigger sudden, very painful, hot swelling. The shoulder is an uncommon site for gout, but pseudogout (calcium crystals) often affects the shoulder in older adults.
• Milwaukee shoulder: a rare, destructive arthritis in older women with large, recurrent, blood-tinged effusions.

Lumps that look like swelling

Not every swelling is inflammation. A soft, rubbery, painless lump that slides under the skin is usually a lipoma, a harmless fatty growth. Cysts (epidermoid or sebaceous) feel firmer and may have a central dot. An AC joint cyst forms over an arthritic AC joint, usually after a long-standing rotator cuff tear.

Serious causes not to miss

Septic arthritis or infected bursa

Bacteria in the shoulder joint destroy cartilage within days. The shoulder is hot, swollen and so painful that moving it even slightly hurts, usually with fever. Risk is higher after a joint injection or surgery, in people with diabetes, rheumatoid arthritis or a weak immune system, and in people who inject drugs. Septic arthritis needs same-day assessment, joint aspiration and IV antibiotics.

Cellulitis

A bacterial skin infection makes the skin red, warm, swollen and tender, with a spreading edge. It is often near a cut, insect bite or eczema patch. Fever and red streaks need urgent treatment.

Blood clot in the arm vein

Upper-limb deep vein thrombosis causes swelling of the whole arm and often the shoulder and chest wall on the same side, with aching, heaviness and visible veins. Causes include IV lines and pacemaker wires, cancer, and repetitive overhead exertion in young athletes (effort thrombosis). A clot can travel to the lungs.

Tumors

A shoulder lump that keeps growing, feels hard or fixed, is deep in the muscle, or is bigger than 5 cm needs imaging to rule out a soft tissue sarcoma. Sarcomas are rare, but "shoulder swelling getting bigger" over weeks is the main warning sign. Bone tumors and cancer that has spread to bone can also cause shoulder swelling with night pain.

Swollen shoulder muscle

Swelling in the muscle itself, rather than the joint, usually follows a strain, a direct blow, an intense new workout or an injection into the deltoid (such as a vaccine). Expect tenderness, tightness and pain when you contract the muscle. It peaks within 1 to 2 days and fades within a week or two. Rarely, extreme exercise causes rhabdomyolysis: severe muscle swelling, weakness and dark, cola-colored urine. That needs urgent care.

Left vs right shoulder swelling

The side matters less than the history. A swollen right shoulder is common simply because most people are right-handed and use it more. Left shoulder pain deserves extra attention because heart pain can spread there, but heart problems cause pain or pressure, not visible swelling. Swelling in the left shoulder blade area is usually a muscle strain, lipoma or cyst.

Symptoms that come with it and what they suggest

• Fever and chills: infection, either septic arthritis, infected bursitis or cellulitis.
• Bruising tracking down the arm: fracture or a significant tear.
• Weakness lifting the arm: rotator cuff tear, or nerve injury after dislocation.
• Numbness or pins and needles: nerve compression, often after dislocation or from the neck.
• Swelling of the hand and arm too: blood clot or lymphedema.
• Several swollen joints and morning stiffness: inflammatory arthritis.

How doctors diagnose the cause

A doctor will ask how and when the swelling started, whether there was an injury, your work and sports, recent injections or surgery, fever, and other joint problems. They will compare both shoulders, feel for warmth, tenderness and lumps, test movement and strength, and check the pulses and sensation in the arm.

Common tests:

• X-ray: for fractures, dislocation, arthritis and calcium deposits.
• Ultrasound: for bursitis, fluid, rotator cuff tears, lumps and arm vein clots.
• Joint aspiration: a needle draws fluid to check for infection, crystals or blood.
• Blood tests: white cell count, CRP and ESR for inflammation, uric acid, and rheumatoid factor if arthritis is suspected.
• MRI: for tendon tears, labral injuries and any lump that needs characterizing.

Treatment and home care

Treatment depends on the cause. For minor strains, overuse and mild bursitis:

1. Rest the shoulder from the activity that triggered it, but keep moving it gently. Complete rest for more than a few days risks a stiff or frozen shoulder, especially over age 40.
2. Ice wrapped in a cloth for 15 to 20 minutes several times a day for the first 48 hours.
3. Pain relief: ibuprofen or naproxen reduce pain and swelling. Follow the label dose. Avoid NSAIDs if you have kidney disease, stomach ulcers or take blood thinners. Acetaminophen (paracetamol) is an alternative.
4. Gentle pendulum exercises: lean forward and let the arm swing in small circles, a few times a day.
5. Heat after the first 2 to 3 days can ease muscle tightness.

Medical treatments include a sling for fractures and separations, physical therapy for rotator cuff problems, steroid injection for persistent bursitis, draining and antibiotics for infection, medicine for gout flares, blood thinners for clots, and surgery for some fractures, complete tears and growing lumps.

Frequently asked questions

What causes a swollen shoulder without injury?

Without an injury, the commonest causes are bursitis from overuse, arthritis, gout or pseudogout, and harmless lumps such as lipomas or cysts. A hot, red swollen shoulder with fever suggests infection and needs same-day care. Swelling of the whole arm suggests a blood clot.

Why is my shoulder swelling getting bigger?

A swelling that grows over hours with heat and pain is usually infection, bleeding or an inflamed bursa. One that grows slowly over weeks or months may be a lipoma, cyst or, rarely, a sarcoma. Any lump that keeps growing, is hard or is larger than 5 cm should be scanned.

How long does a swollen shoulder take to go down?

Swelling from a minor strain or bursitis usually improves within 1 to 2 weeks with rest, ice and anti-inflammatories. Fracture and separation swelling can take 3 to 6 weeks to fade fully. See a doctor if there is no improvement after 2 weeks.

What does swelling on top of the shoulder mean?

A bump or swelling on top of the shoulder usually comes from the AC joint, where the collarbone meets the shoulder blade. Common causes are an AC joint separation after a fall, AC joint arthritis, or a cyst over an arthritic joint.

Can a swollen shoulder be a sign of a blood clot?

Yes, though rarely. A clot in the main arm vein causes swelling of the arm, hand and sometimes the shoulder, with aching and visible veins. It is more likely with an IV line, pacemaker, cancer or heavy overhead exertion. It needs urgent assessment.

Should I use heat or ice on a swollen shoulder?

Use ice for the first 48 hours after an injury or flare, because it limits swelling. After that, heat can relax tight muscles. Never apply heat to a shoulder that is hot and red, since that may be infection.