Shoulder Impingement & ACJ Examination
Impingement syndrome is the most common cause of shoulder pain. Examiners expect you to differentiate between subacromial (extrinsic) impingement and internal (intrinsic) impingement, understand the Neer and Hawkins tests, and recognize ACJ pathology with the cross-body adduction test.
Quick Reference One-Pager
Impingement Stages (Neer)
- Stage I: Edema/hemorrhage (under 25 years, reversible)
- Stage II: Fibrosis/tendinitis (25-40 years)
- Stage III: Bone spurs/tendon rupture (over 40 years)
Impingement Tests
- Neer test (passive forward flexion)
- Hawkins-Kennedy test (IR in 90° flexion)
- Painful arc (60-120°)
- Jobe's test (may be positive)
ACJ Tests
- Cross-body adduction
- ACJ palpation tenderness
- O'Brien's test (also tests labrum)
- Paxinos test
Key Differentiators
- Painful arc location (subacromial 60-120°, ACJ above 120°)
- Local anesthetic injection response
- X-ray findings (ACJ OA, subacromial spurs)
Introduction
Key Concepts
Subacromial Impingement Syndrome:
- Mechanical compression of rotator cuff under coracoacromial arch
- Most common cause of shoulder pain in adults
- Spectrum from tendinitis to full-thickness tears
Causes of Impingement:
- Extrinsic: Structural narrowing (type III acromion, AC osteophytes, os acromiale)
- Intrinsic: Tendon degeneration, weakness, overhead activities
- Secondary: Instability, scapular dyskinesia
ACJ Pathology:
- Common site of OA (especially in laborers, weightlifters)
- May coexist with impingement
- Can be primary pain generator or contribute to impingement
Clinical Assessment
History Clues
Subacromial Impingement:
- Pain with overhead activities
- Night pain (lying on affected side)
- Painful arc with arm elevation
- Gradual onset (unless acute on chronic)
- May have weakness if cuff involved
ACJ Pain:
- Pain localized to "top of shoulder"
- Aggravated by cross-body reaching
- Pain with overhead pressing (gym)
- May have clicking or grinding
Impingement Tests
Special test
Neer Impingement Test
Subacromial impingement
Technique
- 1Patient seated or standing
- 2Examiner stabilizes scapula with one hand
- 3Passively forward flex arm to maximum (thumb pointing down)
- 4Greater tuberosity impinges under anterior acromion
Positive Sign
Pain reproduced at end of forward flexion
Indicates
Subacromial impingement (anterior acromion compression)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
Hawkins-Kennedy Test
Subacromial impingement
Technique
- 1Patient seated or standing
- 2Arm forward flexed to 90°, elbow flexed 90°
- 3Forcibly internally rotate the shoulder (push forearm down)
Positive Sign
Pain reproduced with internal rotation
Indicates
Subacromial impingement (greater tuberosity impinges under coracoacromial ligament)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Neer vs Hawkins:
- Both test subacromial impingement
- Neer: Anterior acromion compression (pure forward flexion)
- Hawkins: Coracoacromial ligament compression (flexion + IR)
- Using both increases sensitivity (if either positive)
Special test
Painful Arc Test
Subacromial pathology
Technique
- 1Patient actively abducts arm from side to overhead
- 2Observe for pain throughout the arc of motion
Positive Sign
Pain between 60-120° abduction (subacromial arc)
Indicates
Subacromial impingement. Pain above 120° suggests ACJ pathology
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
Neer Impingement Injection Test
Confirm subacromial source of pain
Technique
- 1Perform Neer test - note pain level
- 2Inject 10ml local anesthetic into subacromial space
- 3Wait 5-10 minutes
- 4Repeat Neer test
Positive Sign
Significant reduction in pain (greater than 50%)
Indicates
Confirms subacromial space as pain source (diagnostic and therapeutic)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
ACJ Tests
Special test
Cross-Body Adduction Test
ACJ pathology
Technique
- 1Patient seated or standing
- 2Arm forward flexed to 90°
- 3Passively adduct arm across body toward opposite shoulder
Positive Sign
Pain localized to ACJ (top of shoulder)
Indicates
ACJ arthritis, ACJ sprain, or distal clavicle pathology
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
ACJ Palpation
ACJ pathology
Technique
- 1Identify ACJ (palpate along clavicle to lateral end)
- 2ACJ is approximately 2-3cm medial to lateral shoulder edge
- 3Apply direct pressure to joint
Positive Sign
Point tenderness directly over ACJ
Indicates
ACJ arthritis, sprain, or osteolysis
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
O'Brien's Test (Active Compression)
ACJ pathology and superior labral (SLAP) lesions
Technique
- 1Arm forward flexed 90°, adducted 10-15° across midline
- 2Elbow fully extended, thumb pointing DOWN (pronated)
- 3Patient resists downward pressure
- 4Repeat with thumb UP (supinated)
Positive Sign
Pain with thumb DOWN that is relieved with thumb UP. Pain at ACJ = ACJ pathology. Deep pain = SLAP lesion
Indicates
ACJ pathology (superficial pain) or SLAP tear (deep pain)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
Paxinos Test
ACJ pathology
Technique
- 1Patient seated, arm relaxed at side
- 2Examiner places thumb under posterolateral acromion
- 3Index and middle fingers over mid-clavicle
- 4Apply anterosuperior pressure with thumb while pushing down on clavicle
Positive Sign
Pain reproduced at ACJ
Indicates
ACJ pathology
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Internal Impingement
Internal (Posterosuperior) Impingement
Definition:
- Impingement of articular surface of rotator cuff against posterosuperior glenoid
- Occurs in late cocking phase of throwing
Population:
- Young overhead athletes (throwers, swimmers, tennis)
- Different from subacromial impingement
Examination:
- Pain in apprehension position (90° abduction, maximum external rotation)
- Posterior shoulder pain (not anterolateral like subacromial)
- May have GIRD (glenohumeral internal rotation deficit)
Special test
Posterior Impingement Test
Internal (posterosuperior) impingement
Technique
- 1Patient supine, shoulder at edge of bed
- 2Arm abducted 90-110°, elbow flexed 90°
- 3Maximally externally rotate the arm
- 4Apply gentle anterior to posterior pressure on proximal humerus
Positive Sign
Posterior shoulder pain reproduced
Indicates
Internal impingement (articular cuff impinges on posterosuperior glenoid)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Differential Diagnosis
- painLocation
- Anterolateral
- painfulArc
- 60-120°
- tests
- Neer +, Hawkins +
- painLocation
- Top of shoulder
- painfulArc
- Above 120°
- tests
- Cross-body +, ACJ tender
- painLocation
- Anterolateral
- painfulArc
- Yes
- tests
- Weakness, lag signs if complete
- painLocation
- Anterolateral (acute)
- painfulArc
- Variable
- tests
- Severe pain, X-ray shows calcification
- painLocation
- Global
- painfulArc
- No (stiff)
- tests
- Global restriction, ER most limited
- painLocation
- Radiating
- painfulArc
- No
- tests
- Spurling's +, dermatomal pattern
Summary Presentation
“52-year-old painter with 6-month history of right shoulder pain, worse with overhead work.”
Impingement vs ACJ Pain
- impingement
- Anterolateral deltoid
- acj
- Top of shoulder (localized)
- impingement
- 60-120° (mid-arc)
- acj
- Above 120° (high arc)
- impingement
- Yes (lying on side)
- acj
- Less common
- impingement
- Neer, Hawkins
- acj
- Cross-body adduction
- impingement
- Greater tuberosity tender
- acj
- ACJ directly tender
- impingement
- Subacromial injection helps
- acj
- ACJ injection helps
Examiner Tips
Do
- Perform both Neer AND Hawkins
- Note painful arc location (mid vs high)
- Palpate ACJ directly
- Test rotator cuff strength
- Mention injection test as diagnostic option
Don't
- Confuse subacromial and ACJ pain
- Miss internal impingement in throwers
- Forget to assess rotator cuff integrity
- Ignore cervical spine as referral source
- Rely on single test - use combination