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# Subacromial impingement syndrome

Subacromial impingement is shoulder pain from the rotator cuff tendons and bursa being pinched under the roof of the shoulder as the arm is raised.

Updated 2026-10-29

## Structures involved

Tap one to see what it is and open it in 3D.

- [Supraspinatus](https://durgical.com/en/anatomy/supraspinatus/)
- [Subacromial bursa](https://durgical.com/en/anatomy/subacromial-subdeltoid-bursa/)
- [Coracoacromial ligament](https://durgical.com/en/anatomy/coracoacromial-ligament/)
- [Scapula](https://durgical.com/en/anatomy/scapula/)
- [Humerus](https://durgical.com/en/anatomy/humerus/)
- [Biceps (long head)](https://durgical.com/en/anatomy/biceps-brachii-long-head/)
- [Infraspinatus](https://durgical.com/en/anatomy/infraspinatus/)
- [Middle deltoid](https://durgical.com/en/anatomy/deltoid-middle-part/)
- [AC capsule](https://durgical.com/en/anatomy/acromioclavicular-joint-capsule/)

## In the clinical exam

- [Shoulder tests: Neer, Hawkins, Jobe and drop arm](https://durgical.com/en/clinical-exam/shoulder-tests-neer-hawkins-jobe-and-drop-arm/)

## What it is

Shoulder pain caused by compression and irritation of the rotator cuff tendons (mainly [supraspinatus](https://durgical.com/en/anatomy/supraspinatus/)) and the [subacromial bursa](https://durgical.com/en/anatomy/subacromial-subdeltoid-bursa/) beneath the coracoacromial arch when the arm is raised.

## Who gets it

One of the most common causes of shoulder pain in adults seen in primary care, frequent in people who work or play sport with the arm overhead.

## Causes

- Repetitive overhead activity in work or sport
- Structural narrowing of the subacromial space: curved or hooked acromion, acromioclavicular osteophytes, thickened [coracoacromial ligament](https://durgical.com/en/anatomy/coracoacromial-ligament/)
- Functional causes: rotator cuff weakness, scapular dyskinesis, glenohumeral instability
- Age-related degeneration of the rotator cuff tendons

## Risk factors

- Overhead work or sports (swimming, volleyball, throwing)
- Age over 40
- Hooked or downward-sloping acromion
- Acromioclavicular joint arthritis
- Poor posture and weak scapular stabilisers

## Pathophysiology

The coracoacromial arch (acromion, coracoacromial ligament and coracoid process) forms a rigid roof over the [supraspinatus tendon](https://durgical.com/en/anatomy/supraspinatus-tendon/) and subacromial bursa. When the space narrows, raising the arm compresses these tissues, causing bursitis and tendinopathy. Repeated compression can progress to fibrosis, bone spurs and partial or full-thickness cuff tears.

## Classification

- Primary (structural, outlet) vs secondary (functional, from instability or scapular dyskinesis)
- Neer stages: I oedema and haemorrhage; II fibrosis and tendinitis; III bone spurs and tendon tear
- Acromion shape (Bigliani): type I flat, II curved, III hooked

## Symptoms and signs

- Pain over the front and side of the shoulder, often radiating to the deltoid region
- Painful arc, typically between about 60 and 120 degrees of abduction
- Pain with overhead activity and reaching
- Night pain, especially lying on the affected shoulder
- Weakness that is mostly due to pain

## Red flags

- Sudden loss of active elevation after trauma: consider acute rotator cuff tear
- Fever with a hot, swollen joint: consider septic arthritis
- Constant pain with weight loss: consider tumour

## Diagnosis

**Clinical**
Neer sign (pain on passive forward flexion with the [scapula](https://durgical.com/en/anatomy/scapula/) stabilised) and Hawkins-Kennedy test (pain on internal rotation with the shoulder and elbow flexed to 90 degrees); a painful arc; relief after subacromial local anaesthetic (Neer impingement test).

**Tests**
No laboratory test is needed; tests are used only if infection or inflammatory disease is suspected.

**Imaging**
X-rays (including an outlet view) show acromion shape, spurs and acromioclavicular arthritis; ultrasound or MRI assess the bursa and cuff tendons for tears.

## Differential diagnosis

- Rotator cuff tear
- Frozen shoulder (adhesive capsulitis)
- Acromioclavicular joint arthritis
- Calcific tendinitis
- Long head of biceps tendinopathy
- Cervical radiculopathy

## Goal of treatment

Relieve pain, restore normal shoulder and scapular mechanics, and prevent progression to rotator cuff tearing.

## Treatment

**Conservative**
Relative rest and modification of overhead activities, with ice in the acute phase.

**Medical**
Non-steroidal anti-inflammatory drugs for short periods to control pain.

**Rehabilitation**
Physiotherapy to strengthen the rotator cuff and scapular stabilisers and correct posture; the mainstay of treatment.

**Procedure**
Subacromial corticosteroid injection for short-term relief when pain limits rehabilitation.

**Surgical**
Arthroscopic subacromial decompression (acromioplasty) when prolonged rehabilitation fails; its benefit over physiotherapy is debated.

## Complications

- Partial or full-thickness rotator cuff tear
- Chronic shoulder pain and loss of function
- Secondary shoulder stiffness
- Complications of injection or surgery (infection, tendon weakening)

## Prognosis

Most patients improve with activity modification and a structured exercise programme over several months. Recurrence is common if overhead loading resumes without correcting the mechanics.

## Prevention

- Progressive strengthening of the rotator cuff and scapular muscles
- Good technique and posture in overhead sport and work
- Gradual increase in overhead training load

## Test yourself

Think of the answer, then tap the question to see it.

## Which three structures form the coracoacromial arch?

The acromion, the coracoacromial ligament and the coracoid process.

## How is the Hawkins-Kennedy test performed?

Shoulder and elbow flexed to 90 degrees, the examiner internally rotates the arm; pain suggests subacromial impingement.

## What does the Neer sign involve?

Passive forward flexion of the internally rotated arm while the scapula is stabilised; pain suggests impingement.

## Which rotator cuff tendon is most often affected in subacromial impingement?

The supraspinatus tendon, which runs under the coracoacromial arch.

## What is the painful arc of impingement?

Pain during mid-range abduction, typically about 60 to 120 degrees, that eases above and below that range.

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/conditions/subacromial-impingement-syndrome/)

## Related conditions

- [Rotator cuff tear](https://durgical.com/en/conditions/rotator-cuff-tear/)
- [Frozen shoulder (adhesive capsulitis)](https://durgical.com/en/conditions/frozen-shoulder/)
- [Cervical radiculopathy](https://durgical.com/en/conditions/cervical-radiculopathy/)
- [Biceps tendon rupture](https://durgical.com/en/conditions/biceps-tendon-rupture/)
- [Winged scapula](https://durgical.com/en/conditions/winged-scapula/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Shoulder Impingement Syndrome](https://www.ncbi.nlm.nih.gov/books/NBK554518/) (StatPearls (NCBI Bookshelf), 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/conditions/subacromial-impingement-syndrome/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/subacromial-impingement-syndrome/