How do you assess for a rotator cuff injury?

Assessment of Rotator Cuff Injury

Begin with plain radiographs (AP views in internal and external rotation plus axillary or scapular Y view) to exclude fractures and dislocations, then proceed directly to MRI shoulder without IV contrast for definitive diagnosis of rotator cuff pathology. 1, 2

Initial Clinical Evaluation

History and Physical Examination Findings

Key symptoms that suggest rotator cuff injury include:

• Pain in the anterior or anterolateral shoulder worsening with overhead activities (sensitivity 88%, specificity 33%) 3
• Severe night pain is characteristic of full-thickness tears 2, 4
• Focal weakness in the affected shoulder (present in 75% of cases) 3
• Decreased range of motion, particularly during abduction with external or internal rotation 3
• History of traumatic fall (especially on outstretched arm) or repetitive overhead activities increases likelihood of tear 1, 2

Critical physical examination tests:

• Supraspinatus weakness (empty can test) indicates supraspinatus involvement and suggests full-thickness tear 2, 5
• Weakness of external rotation is highly predictive when combined with other findings 5
• Neer's impingement test (sensitivity 88%, specificity 33%) 3
• Hawkins' impingement test (sensitivity 92%, specificity 25%) 3
• Positive "shrug sign" (inability to actively elevate arm) suggests significant tear 4

The combination of 3 positive clinical tests (supraspinatus weakness, external rotation weakness, and impingement signs) or 2 positive tests in patients >60 years is highly predictive of rotator cuff tear. 5

Imaging Algorithm

Step 1: Plain Radiographs (Always First)

Obtain AP views in internal and external rotation plus axillary or scapular Y view to exclude fractures, dislocations, glenohumeral instability, and assess for osseous abnormalities like acromion morphology and acromioclavicular joint disease. 1, 3

• Reduced acromiohumeral interval (<7mm) is a direct radiographic sign of rotator cuff rupture 6
• Failure to obtain axillary or scapular Y views can result in missed dislocations that appear normal on AP views alone 2

Step 2: MRI Shoulder Without IV Contrast (Primary Advanced Imaging)

MRI shoulder without IV contrast is the optimal next imaging study for suspected rotator cuff tears, with 98% sensitivity for any rotator cuff tear and 94% sensitivity with 93% specificity for full-thickness tears. 1, 2, 3

Why MRI without contrast is preferred:

• Best modality for assessing soft tissue injuries including rotator cuff, labral, and cartilage pathology, particularly in acute trauma 1, 2
• High sensitivity and specificity for full-thickness tears (90-91% sensitivity, 93-95% specificity) comparable to MR arthrography 1, 2
• Post-traumatic joint effusion in acute settings provides natural joint distention, enhancing soft tissue visualization without need for arthrography 2
• Assesses critical prognostic factors: tendon retraction, muscle atrophy, and fatty infiltration that guide surgical decision-making 1, 2

MRI findings diagnostic of rotator cuff tears:

• Full-thickness tear: Increased signal intensity extending from inferior to superior tendon surface on all sequences 1
• Partial-thickness tears: Can occur at articular surface (most common), bursal surface, or intrasubstance 1
• Tendinosis/tendinopathy: Tendon enlargement with heterogeneous signal (increased T1, slightly increased T2) without focal disruption 1

Alternative Imaging Modalities

Ultrasound shoulder:

• Equivalent to MRI for detecting full-thickness rotator cuff tears (90% sensitivity, 93-95% specificity) when local expertise is available 1, 3
• Major limitations: Variable interobserver agreement for partial-thickness tears, operator-dependent performance, limited by acute pain restricting range of motion, and cannot assess other intra-articular pathologies like labral tears 1, 2, 3
• May be preferred over MRI in patients with proximal humeral hardware causing MRI artifacts or large body habitus 1

MR arthrography:

• Reserved for equivocal cases when conventional MRI cannot distinguish between full-thickness and partial-thickness tears 1, 2
• Higher sensitivity than non-contrast MRI for partial-thickness articular surface tears 1, 2, 3
• Not indicated as initial study in acute trauma because post-traumatic effusion already provides joint distention 2

Critical Pitfalls to Avoid

• Do not proceed to orthopedic referral without advanced imaging - MRI is essential to confirm diagnosis, characterize tear extent, assess tendon quality, and guide treatment planning 2
• Do not use CT without contrast for rotator cuff evaluation - it cannot assess soft tissue pathology in acute settings 1, 2, 3
• Do not use bone scan or FDG-PET/CT - these modalities cannot describe tear extent or degree of muscle atrophy 1, 2, 3
• Do not order MRI with IV (non-arthrographic) contrast - standard intravenous gadolinium provides no additional diagnostic benefit for rotator cuff tears and unnecessarily exposes patients to contrast-related risks 2
• Avoid gadolinium-based contrast in dialysis-dependent patients or those with severe renal dysfunction (GFR <30 mL/min/1.73 m²) due to nephrogenic systemic fibrosis risk 2
• Remember that 10% of rotator cuff tears are asymptomatic and present only with morphologic changes on imaging 1

Special Populations

In youth/adolescent throwing athletes (<18 years):

• Undersurface tears from overuse are more common than primary impingement, often resulting from atraumatic microinstability and weak rotator cuff muscles 2, 3
• Little Leaguer shoulder (proximal humeral physeal stress injury) occurs in skeletally immature pitchers aged 11 to early teenage years 2

In patients with prior rotator cuff repair:

• MRI without contrast, MR arthrography, and ultrasound are all rated as equally appropriate (rating 9/9) for evaluating suspected retear, depending on local expertise 1