Subacromial bursa !
The subacromial bursa is a thin fluid sac under the roof of the shoulder; it lets the rotator cuff tendons glide and can become inflamed.
Official name: Subacromial-subdeltoid bursa
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What it is
A thin fluid-filled sac between the rotator cuff and the acromion and deltoid.
What it does
Lets the cuff tendons glide under the roof of the shoulder.
Key facts
- Where
- Between the acromion, coracoacromial ligament and deltoid above and the supraspinatus tendon below; continuous with the subdeltoid bursa
- Function
- Lets the cuff glide under the arch; inflamed in impingement
Relations
- Above
- Acromion, coracoacromial ligament and deltoid (its subdeltoid part)
- Below
- Supraspinatus tendon and the shoulder capsule: the top of the rotator cuff is its floor
- Lateral
- Extends under the deltoid over the greater tuberosity as the subdeltoid bursa
How to find it
Not felt when normal. Tenderness just below the front edge of the acromion, with the arm extended behind the back to bring the supraspinatus insertion forward, points to the bursa and cuff; injection uses a posterior or lateral path under the acromion.
Examination
- Neer sign: pain on passive forward elevation with the arm turned inward suggests impingement
- Hawkins–Kennedy test: pain on internal rotation with shoulder and elbow flexed to 90° suggests subacromial impingement
- Painful arc: pain in mid-abduction that eases above it suggests subacromial disease; pain only at the top of the arc points rather to the AC joint
On imaging
On ultrasound the normal bursa is a thin dark line under the deltoid; bursitis shows thickening or fluid, and dynamic scanning shows the bursa bunching under the acromion as the arm lifts. MRI shows fluid and the state of the cuff.
Common problems
- Bursitis: the bursa swells and hurts under the acromion, often with impingement or a cuff tendon problem.
- Night pain lying on the shoulder and pain lifting the arm.
How it is diagnosed
Impingement tests and pain relief after a numbing injection into the bursa. Ultrasound or MRI shows fluid and the cuff.
Treatment
- Rest from overhead activity, anti-inflammatory medicines and physical therapy.
- Steroid injection into the bursa.
- Arthroscopic bursa removal, usually as part of a rotator cuff repair.
Clinical notes
- Calcific deposits in the supraspinatus can rupture into the bursa, causing sudden severe pain
- Arthroscopic subacromial decompression removes the bursa and may shave the underside of the acromion; its benefit over rehabilitation alone is debated
- Subacromial injection that relieves pain (Neer impingement test) helps separate cuff pain from pain coming from the neck or the joint
Anatomical variants
- Acromion shape: flat, curved or hooked (Bigliani types I–III); the hooked shape is linked to impingement
- Os acromiale, an unfused acromial apophysis, in a minority of people
Development
The acromion ossifies from several centres that appear in adolescence and usually unite by the mid-20s; an unfused segment (os acromiale) can move with deltoid pull and crowd the bursa and cuff below it.
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
Where is the subacromial bursa?
Between the acromion, coracoacromial ligament and deltoid above and the supraspinatus tendon below; continuous with the subdeltoid bursa.
What does contrast reaching the subacromial bursa on shoulder arthrography mean?
A full-thickness rotator cuff tear, since the bursa normally does not communicate with the joint.
What is the Hawkins–Kennedy test for the subacromial bursa?
Pain on internal rotation with the shoulder and elbow flexed to 90° suggests subacromial impingement.
What causes sudden severe pain in the subacromial bursa in calcific tendinitis?
Calcific deposits in the supraspinatus rupturing into the bursa.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- bursa subacromialis TA2 2557
- Official Spanish (DeCS)
- Bolsas subacromial y subdeltoidea
- English (TA2)
- Subacromial-subdeltoid bursa
Related
Sources: Terminologia Anatomica (TA2); Anatomy, Shoulder and Upper Limb, Shoulder; Anatomy, Rotator Cuff.
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Representative model, for educational purposes only.
