Not in itself. It is fluid in a lubricating cushion. What matters is what the bursa is reacting to — most often the rotator cuff — and that is the part of the report worth reading closely.

How long does it take to settle?

Weeks to several months. It depends on the cause: bursitis alongside straightforward tendinopathy often settles within a few months of proper rehabilitation, while a shoulder with a significant cuff tear follows the tear’s timeline.

Why does my report mention both bursitis and the rotator cuff?

Because they sit directly on top of each other and one usually explains the other. A degenerate or torn tendon irritates the bursa above it, so the two are described together in the same paragraph.

Should I have a cortisone injection?

It often helps, and it works best as a way to make rehabilitation possible rather than as the treatment on its own. Ask what the plan is for the weeks after the injection — if there is not one, the pain relief tends to be temporary.

What does a lot of fluid in the bursa mean?

It raises the question of a full-thickness rotator cuff tear, because a tear connects the joint to the bursa and lets fluid move up into it. A radiologist looking at the images will usually address that directly in the same report.

Findings explained

What “subacromial-subdeltoid bursitis” means

Read Your Scan Editorial Team·Last updated 10 September 2026·5 min read

Written from published radiology references and reviewed for plain language. Not written or signed by a physician, and not a diagnosis. How we write these pages →

Coronal MRI of the shoulder — A real coronal MRI of the shoulder — the view the bursa is assessed on. It is the thin layer between the rotator cuff tendon and the bony shelf above it, and it is only conspicuous when it contains fluid.Real exam · RSatUSZ · CC BY-SA 4.0

The short answer

The subacromial-subdeltoid bursa is a thin cushion that sits between the rotator cuff tendons and the bone above them. "Bursitis" on a report means fluid has collected in it or its lining has thickened. It is rarely a problem in its own right: in most shoulders it is reacting to something underneath, usually the rotator cuff, so the useful question is what the rest of the report says.

The bursa is a lubricating cushion, not a joint. It lets the rotator cuff glide under the bone above it.
A small amount of fluid in it is normal and is reported in shoulders that do not hurt.
It is usually secondary. Isolated bursitis with a completely normal cuff is uncommon.
A large amount of fluid in the bursa can be a clue that the rotator cuff is torn through, letting joint fluid leak upwards.
The treatment is aimed at what caused it, though an injection into the bursa often relieves symptoms while that is sorted out.

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What a bursa is

Wherever a tendon has to slide against a bone, the body puts a bursa between them: a flat, closed sac with a slippery lining and a trace of fluid inside. It is a bearing surface.

The subacromial-subdeltoid bursa is one of the largest in the body. It lies above the rotator cuff tendons and below the acromion — the bony shelf at the top of the shoulder — and extends outwards under the deltoid muscle, which is where the double-barrelled name comes from. It is not one bursa and then another; it is a single space with two regions.

A trace of fluid in this bursa is normal and appears in reports on shoulders that have never hurt. The report is describing a quantity, and only a radiologist looking at the images can say whether that quantity is beyond usual.

Why it fills up

Because it is reacting to something. The bursa sits in a narrow space, and almost anything that irritates or narrows that space produces fluid in it.

What is underneath	Why the bursa reacts
Rotator cuff tendinopathy	A thickened, degenerate tendon rubbing in a tight space irritates the bursa above it. The commonest pairing by far.
A partial rotator cuff tear	The damaged tendon surface irritates the bursa directly.
A full-thickness cuff tear	The tear connects the joint below to the bursa above, so joint fluid moves into it. A lot of bursal fluid raises this question.
Impingement from bone spurs	Spurs on the underside of the acromion or the AC joint narrow the space the bursa has to occupy.
Calcific tendinopathy	Calcium deposits in the tendon can leak into the bursa and produce an intense, sudden reaction.
Inflammatory arthritis	The lining of the bursa is inflamed as part of a wider process, usually with other joints involved.

That table is the point of the whole post. If your report names bursitis, read the next sentence about the rotator cuff — that is usually where the actual finding is.

X-ray of the proximal humerus — The upper arm and shoulder region on a plain X-ray. This is why MRI was ordered: a plain film shows bone well and soft tissue barely at all. The bursa, the tendons and the fluid inside them are all invisible here.Real exam · Hellerhoff · CC BY-SA 4.0

What it feels like

Pain on the outside of the upper arm rather than on the point of the shoulder — which is what separates it from AC joint pain.
Pain on lifting the arm out to the side, classically in the middle part of that arc.
Pain lying on that side at night, often the symptom people mention first.
Difficulty reaching overhead or behind the back.

None of that distinguishes bursitis from rotator cuff problems, because in most shoulders they are the same problem seen from two angles.

What usually happens next

Physiotherapy first, aimed at the rotator cuff and at how the shoulder blade moves, because that is what changes the space the bursa lives in. Relative rest from the aggravating movements, and analgesia as needed.

A corticosteroid injection into the bursa is common and frequently effective. It is worth understanding what it does: it reduces the pain enough to let rehabilitation happen, rather than fixing the tendon underneath. An injection without a rehabilitation plan tends to buy months, not a cure.

Surgery — usually shaving bone from the underside of the acromion to widen the space, sometimes with cuff repair — is for shoulders that do not improve after a proper course of physiotherapy. The evidence for decompression alone in shoulders with an intact cuff has been challenged in recent trials, which is worth knowing if it is proposed.

Frequently asked questions

Is bursitis serious?: Not in itself. It is fluid in a lubricating cushion. What matters is what the bursa is reacting to — most often the rotator cuff — and that is the part of the report worth reading closely.
How long does it take to settle?: Weeks to several months. It depends on the cause: bursitis alongside straightforward tendinopathy often settles within a few months of proper rehabilitation, while a shoulder with a significant cuff tear follows the tear’s timeline.
Why does my report mention both bursitis and the rotator cuff?: Because they sit directly on top of each other and one usually explains the other. A degenerate or torn tendon irritates the bursa above it, so the two are described together in the same paragraph.
Should I have a cortisone injection?: It often helps, and it works best as a way to make rehabilitation possible rather than as the treatment on its own. Ask what the plan is for the weeks after the injection — if there is not one, the pain relief tends to be temporary.
What does a lot of fluid in the bursa mean?: It raises the question of a full-thickness rotator cuff tear, because a tear connects the joint to the bursa and lets fluid move up into it. A radiologist looking at the images will usually address that directly in the same report.

When you want a second read of the images themselves

Understanding your radiologist’s report is free. A Second Opinion is the other thing: an independent AI reading of your images, done from the pictures rather than from the report, with the differences called out and a Q&A on the result. It is informational — not a diagnosis, and not a substitute for your doctor.

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Words on this page

Each of these has its own page in the report glossary.

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Sources

Patient-facing procedure descriptions (MRI, CT, X-ray, ultrasound)RadiologyInfo.org — Radiological Society of North America & American College of Radiology
MRI scan — overview, how it is performed and resultsNHS (United Kingdom)
ACR Appropriateness Criteria and practice parameters for reportingAmerican College of Radiology

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Read Your Scan is informational only — not a medical diagnosis, and not a substitute for a licensed radiologist or your doctor. This page explains what a report says and what a radiologist looks at; it cannot tell you what your own images show. If you have urgent symptoms, seek care.