What are the signs and symptoms of subacromial impingement syndrome?

Signs and Symptoms of Subacromial Impingement Syndrome

Subacromial impingement syndrome (SIS) is characterized primarily by anterior or anterolateral shoulder pain during arm elevation and overhead activities, with pain during the arm cocking and acceleration phases of throwing motions being particularly common. 1

Primary Clinical Manifestations

• Pain located in the anterior or anterolateral aspect of the shoulder that worsens with overhead activities 1
• Pain during specific phases of throwing motions (arm cocking and acceleration phases) in athletes 1
• Decreased range of motion, particularly during abduction with external or internal rotation 1
• Focal weakness in the affected shoulder 1
• Pain during the Hawkins' test (forcible internal rotation with the arm flexed forward at 90 degrees) - 92% sensitive but only 25% specific for impingement 1
• Pain during the Neer's test (pain with full forward flexion between 70-120 degrees) - 88% sensitive but only 33% specific for impingement 1

Pathophysiological Signs

• Supraspinatus tendon irritation due to subacromial outlet obstruction 1
• Difficulty for the humeral head to stay centered in the glenoid fossa during arm motion (in secondary impingement) 1
• Rotator cuff weakness combined with ligamentous laxity (particularly in younger athletes) 1
• Scapular dyskinesis - poor coordination of scapular movements during arm elevation 1
• Impingement of the supraspinatus tendon between the humeral head and coracoacromial arch during abduction 1

Advanced or Chronic Signs

• Progressive decrease in velocity and precision in throwing athletes 1
• Tendon degeneration with possible progression to rotator cuff tears if left untreated 1
• Weakness of posterior shoulder musculature combined with overdeveloped anterior musculature in athletes 1
• Possible development of subacromial bursitis 2

Diagnostic Imaging Findings

• Morphological abnormalities of the acromion process (curved or hooked types are more associated with impingement) 3
• MRI may show soft tissue abnormalities in the supraspinatus tendon, subacromial bursa, and biceps tendon 1
• Ultrasound can detect rotator cuff abnormalities and is equivalent to MRI for this evaluation 1

Important Considerations

• SIS represents a spectrum of pathology ranging from subacromial bursitis to rotator cuff tendinopathy and potentially full-thickness rotator cuff tears 4
• The condition may be caused by extrinsic compression or intrinsic degeneration of the rotator cuff tendons 2, 4
• No single clinical test is definitive for SIS; a combination of clinical tests is required for accurate diagnosis 5
• Meta-analyses show that neither the Neer sign nor the Hawkins sign alone has sufficient diagnostic utility for impingement syndrome 6

Differential Diagnosis Considerations

• Primary vs. secondary impingement (secondary is more common in younger athletes) 1
• Internal impingement (particularly in overhead athletes) vs. subacromial impingement 2
• Rotator cuff tears which may present with similar symptoms but require different management 1
• Subcoracoid impingement which affects anterior soft tissues between the coracoid process and lesser tuberosity 2

Early recognition of these signs and symptoms is crucial for preventing progression to more serious rotator cuff pathology and for implementing appropriate treatment strategies.