How do I assess for a biceps tendon rupture?

Assessment of Biceps Tendon Rupture

For suspected biceps tendon rupture, begin with specific clinical tests—the Hook test combined with biceps crease interval (BCI) measurement achieves 100% specificity for acute complete distal ruptures when both are positive, while MRI remains the gold standard imaging modality with 86.4% accuracy for complete tears and superior detection of partial ruptures. 1, 2, 3

Clinical Examination: Distal Biceps Tendon

Primary Clinical Tests (Perform in Sequence)

For acute complete distal biceps ruptures (≤1 month), use the Hook test + BCI combination:

• Hook test: Patient flexes elbow to 90° with forearm supinated; examiner attempts to "hook" index finger under the lateral edge of the biceps tendon from lateral to medial. Positive test = inability to hook under intact tendon. 3, 4
• BCI measurement: Measure distance from antecubital crease to distal biceps muscle belly. Abnormal if >6 cm or side-to-side difference >2 cm. 3, 4
• When both tests are positive together: 94% sensitivity and 100% specificity for acute complete rupture. 3
• When all three validated tests agree (Hook + BCI + passive forearm pronation), sensitivity and specificity reach 100%. 4

Passive forearm pronation (PFP) test:

• With elbow flexed 90° and forearm supinated, passively pronate the forearm while palpating the biceps tendon. 3, 4
• Positive test = lack of tendon tension/cord-like structure during pronation. 4

Additional Clinical Tests

For partial ruptures or tendinosis:

• Biceps provocation test: 95% sensitivity, 97% specificity, 96% accuracy—the most accurate single test for partial tears. 5
• Resisted hook test: 78% sensitivity, 76% specificity. 5
• Palpation of tendon footprint: 100% sensitivity for partial ruptures. 3

For chronic complete ruptures (>1 month):

• Weakness on active supination: 100% sensitivity for chronic complete ruptures. 3
• Hook test + BCI combination: Maintains 100% specificity in chronic cases. 3

Supination-pronation test (dynamic assessment):

• With intact distal biceps, substantial change in biceps shape occurs: muscle moves proximally with supination, distally with pronation. 6
• Absence of this dynamic movement suggests rupture. 6

Clinical Examination Pitfalls

• Do not rely on strength testing alone—the lacertus fibrosus and brachialis can mask complete ruptures by maintaining some flexion strength. 6
• Isolate supination and pronation to avoid missing ruptures. 6
• Acute swelling and ecchymosis may obscure physical findings—clinical tests remain reliable despite pain. 3, 6

Imaging Strategy

First-Line Imaging

MRI (non-contrast) is the gold standard:

• 86.4% accuracy for complete distal biceps ruptures vs. 45.5% for ultrasound. 1, 2
• 76% sensitivity and 50% specificity for detecting all biceps tendon tears. 1
• Superior for detecting partial tears and tendinopathy compared to ultrasound. 1
• ACR rates MRI as 9/9 (usually appropriate) for suspected biceps tendon pathology. 2

FABS (flexion-abduction-supination) view for distal biceps:

• Patient prone, elbow flexed 90°, shoulder abducted, forearm supinated (thumbs up). 1
• Visualizes entire distal biceps tendon on single image. 1
• Most useful for differentiating high-grade partial from complete tears by identifying subtle residual fibers. 1
• Better interrater reliability than standard MRI views. 1

Ultrasound (operator-dependent alternative):

• ACR rates ultrasound as 9/9 (usually appropriate) when performed by skilled operators. 2
• 62.5% sensitivity and 20% specificity for biceps tendon tears—inferior to MRI. 1
• Equivalent to MRI for complete ruptures in experienced hands, but less reliable for partial tears. 1, 7
• Medial imaging approach preferred with substantial interreader agreement. 1
• Allows dynamic assessment and can be combined with therapeutic injection. 2
• Excellent concordance with surgery (k=0.706) for complete ruptures. 7

When Imaging Is NOT Required

Skip imaging and proceed directly to surgery when:

• Hook test, BCI, and PFP test are ALL positive in agreement. 4
• History and physical examination are consistent with complete rupture. 4
• This approach achieves 100% sensitivity and specificity. 4

When Imaging IS Required

Obtain MRI (preferably with FABS view) when:

• Clinical tests are equivocal or not in agreement. 4
• Partial rupture or tendinosis suspected (requires differentiation for treatment planning). 5, 8
• Chronic presentation where anatomy may be distorted. 3
• MRI distinguishes partial rupture from tendinosis/bursitis, which influences surgical vs. conservative management. 5

Imaging to Avoid

• MR arthrography is rated 1/9 (usually not appropriate) for biceps tendon rupture—natural joint effusion provides sufficient contrast. 2

Proximal (Long Head) Biceps Tendon Rupture

Clinical presentation:

• "Popeye deformity"—visible bulge of retracted biceps muscle belly. 1
• Partial rupture of long head with intact short head is the most common injury pattern. 1
• 89% of atraumatic ruptures involve the long head. 1

Imaging approach:

• MRI and ultrasound both rated 9/9 (usually appropriate) by ACR for proximal biceps pathology. 2
• MRI has improved sensitivity for partial tears of proximal biceps. 1
• Ultrasound equivalent to MRI when performed by skilled operators. 2

Key Diagnostic Algorithm

1. Perform Hook test + BCI measurement + PFP test in all suspected cases. 3, 4
2. If all three tests positive and history consistent: Proceed to surgery without imaging. 4
3. If tests equivocal or suggest partial tear: Obtain MRI with FABS view. 1, 5, 4
4. If chronic presentation (>1 month): Check for weakness on active supination (100% sensitive) and obtain MRI. 3
5. For partial tears: Use biceps provocation test (95% sensitivity) and obtain MRI to differentiate from tendinosis. 5