What special assessment tests can be used to differentiate glenohumeral (shoulder joint) involvement from subacromial (below the acromion) pathology?

Special Assessment Tests to Differentiate Glenohumeral vs Subacromial Pathology

The most reliable and diagnostically accurate special tests for differentiating glenohumeral joint involvement from subacromial pathology are the painful arc test, external rotation resistance test, and empty can test, with a combination of 3 or more positive tests out of 5 standard impingement tests confirming subacromial impingement syndrome. 1

Subacromial Impingement Tests

Most Reliable Individual Tests

1. Painful Arc Test

   • Patient actively abducts arm from 0° to 180°
   • Positive: Pain between 60° and 120° of abduction
   • Diagnostic value: High sensitivity for ruling out SAIS (specificity 87%, +LR 2.25) 1
   • Reliability: Moderate to substantial agreement (kappa 0.45-0.67) 1

2. Empty Can Test (Jobe Test)

   • Patient's arm positioned at 90° abduction, 30° forward flexion, with thumbs pointing down
   • Examiner applies downward pressure while patient resists
   • Positive: Pain or weakness
   • Diagnostic value: Excellent for confirming SAIS (+LR 3.90) 1
   • Reliability: Moderate to substantial agreement 1

3. External Rotation Resistance Test

   • Patient's arms at sides with elbows flexed 90°
   • Examiner applies internal rotation force while patient resists
   • Positive: Pain or weakness
   • Diagnostic value: Best individual test for confirming SAIS (+LR 4.39) 1
   • Reliability: Moderate to substantial agreement 1

Additional Impingement Tests

1. Neer Test

   • Examiner stabilizes scapula while passively flexing patient's arm
   • Positive: Pain with forced flexion
   • Diagnostic value: Good for ruling out SAIS (-LR 0.35) 1
   • Reliability: Fair strength of agreement (kappa 0.39-0.40) 1

2. Hawkins-Kennedy Test

   • Patient's arm flexed 90° at elbow and shoulder, then internally rotated
   • Positive: Pain with internal rotation
   • Diagnostic value: Least reliable of the five tests 1
   • Reliability: Fair strength of agreement (kappa 0.39-0.40) 1

Glenohumeral Joint Tests

1. Anterior Apprehension Test

   • Patient's arm in 90° abduction and external rotation
   • Positive: Apprehension or pain with anterior pressure
   • Indicates: Anterior instability (glenohumeral pathology)

2. Load and Shift Test

   • Examiner applies anterior/posterior pressure to humeral head
   • Positive: Excessive translation or pain
   • Indicates: Glenohumeral instability

3. Sulcus Sign

   • Downward traction applied to arm at side
   • Positive: Gap appears between acromion and humeral head
   • Indicates: Inferior glenohumeral instability

4. Labral Tests (e.g., O'Brien's Test)

   • Arm flexed to 90°, adducted 10-15°, internally rotated
   • Examiner applies downward resistance
   • Positive: Pain that improves with external rotation
   • Indicates: SLAP lesion (glenohumeral pathology)

Diagnostic Algorithm

1. Perform all five impingement tests:

   • Painful arc, Empty can, External rotation resistance, Neer, Hawkins-Kennedy

2. Count number of positive tests:

   • ≥3 positive tests: Confirms subacromial impingement syndrome 1, 2
   • <3 positive tests: Rules out subacromial impingement syndrome 1

3. Best test combination:

   • For confirming SAIS: Painful arc + Empty can + External rotation resistance (when ≥2 are positive) 2
   • For ruling out SAIS: Painful arc + External rotation resistance (when both negative) 2

4. If subacromial tests negative, perform glenohumeral tests

Advanced Imaging Considerations

• MR arthrography: Preferred for suspected labral tears with or without instability (glenohumeral pathology) 3
• MRI without contrast: Appropriate for suspected bursitis or biceps tenosynovitis (subacromial pathology) 3
• Ultrasound: Equivalent to MRI for evaluating subacromial bursitis and biceps tenosynovitis 3

Clinical Pearls

• The Hawkins position results in significantly greater subacromial space narrowing and rotator cuff contact than the Neer position, explaining its utility in detecting subacromial pathology 4
• Limitation of glenohumeral external rotation is strongly associated with subacromial impingement syndrome and correlates with pain severity 5
• Intra-articular contact of the supraspinatus with the posterosuperior glenoid occurs in both Neer and Hawkins positions, suggesting internal impingement may play a role in positive test results 4