What is Subacromial Impingement Syndrome, Left Shoulder
Subacromial impingement syndrome (SIS) of the left shoulder is a condition where the rotator cuff tendons and subacromial bursa become compressed between the humeral head and the acromion process during arm elevation, causing pain and functional limitation. 1
Pathophysiology
SIS represents a spectrum of pathology that includes:
- Subacromial bursitis (inflammation of the bursa)
- Rotator cuff tendinopathy (tendon degeneration/inflammation)
- Partial or full-thickness rotator cuff tears 1
The condition results from reduction of the subacromial space, leading to chronic entrapment and repeated trauma to these structures 2. This is the most common diagnosis for shoulder pain 3.
Underlying Mechanisms
Multiple factors contribute to SIS, either alone or in combination 4:
Anatomical factors:
- Inflammation of tendons and bursa
- Degeneration of rotator cuff tendons
- Bony abnormalities (acromial spurs, low-lying acromion, hooked/curved acromion shape)
- Acromioclavicular joint degeneration
- Posterior glenohumeral capsule tightness
Functional factors:
- Weak or dysfunctional rotator cuff muscles
- Weak or dysfunctional scapular muscles
- Abnormal glenohumeral and scapulothoracic movement patterns
- Postural dysfunctions
Recent evidence shows that lateral acromial spurs (especially birdbeak type) are significantly associated with increased shoulder pain and disability 5, while rotator cuff pathologies combined with reduced subacromial space act as primary causes 6.
Clinical Presentation
Common symptoms include:
- Shoulder pain, particularly with overhead activities
- Pain at night
- Limited range of motion
- Functional loss in daily activities
- Progressive weakness if rotator cuff tear develops
The diagnosis is often delayed until a complete rotator cuff tear has occurred 2, making early recognition critical for preventing progression.