What is the likely diagnosis and recommended management for a 34‑year‑old man with acute left upper‑arm pain, swelling for two days, a bruised left elbow, and a sensation of a tear after lifting a heavy couch?

Likely Diagnosis: Distal Biceps Tendon Rupture

This 34-year-old man with acute upper arm pain, a palpable "tear" sensation during heavy lifting, and bruising at the elbow most likely has a distal biceps tendon rupture, which requires urgent imaging confirmation and orthopedic referral for surgical repair within 3-4 weeks to optimize outcomes. 1, 2

Clinical Reasoning

The presentation is classic for distal biceps injury:

• Middle-aged male (most common demographic) 3
• Acute traumatic mechanism with eccentric load during lifting 3
• Sensation of "tear" (pathognomonic for tendon rupture) 1
• Bruising at elbow (indicates significant soft tissue injury) 1

The location of bruising at the elbow rather than mid-upper arm, combined with the lifting mechanism, strongly suggests distal biceps involvement rather than proximal biceps or other muscle injuries. 4, 1

Immediate Diagnostic Workup

Step 1: Plain Radiographs First

Order AP and lateral radiographs of the elbow immediately to exclude fractures, avulsion injuries, or bony abnormalities before proceeding with soft tissue imaging. 4, 1

• Radiographs may show avulsion fractures at the radial tuberosity (biceps insertion site) 4
• Joint effusion with fat pad signs could indicate associated intra-articular pathology 4

Step 2: MRI Without Contrast (Preferred)

If radiographs are normal or indeterminate, proceed directly to MRI without contrast using the FABS view (flexion-abduction-supination positioning). 4, 1

• MRI has 86.4% accuracy for biceps tendon tears, significantly superior to ultrasound's 45.5% accuracy 1
• The FABS view provides optimal visualization of the entire distal biceps tendon on a single image 4, 1
• MRI reliably distinguishes partial from complete tears, which is critical for treatment planning 4, 1

Alternative: Ultrasound (If MRI Unavailable)

Ultrasound can be considered when MRI is contraindicated or unavailable, but has significant limitations. 4, 1

• Sensitivity/specificity for complete tears: 81%/91% 4
• Poor performance for partial tears and tendinopathy 1
• Operator-dependent with variable accuracy 4

Critical Management Decisions

Complete Rupture (Most Likely)

Urgent orthopedic referral for surgical repair within 3-4 weeks of injury. 2

• Surgical repair is the mainstay of treatment for complete tears 3
• Delayed repair beyond 3-4 weeks may require tendon reconstruction with graft rather than primary repair 3
• Non-operative management results in permanent loss of supination and flexion strength 2, 3

Partial Rupture (Less Likely Given Presentation)

Conservative management with immobilization can be considered for confirmed partial tears on MRI. 2

• Requires MRI confirmation—clinical examination alone is insufficient 1, 2
• Immobilization followed by progressive rehabilitation 2

Common Pitfalls to Avoid

Do not rely on ultrasound alone for definitive diagnosis—its 45.5% accuracy for biceps tears is inadequate for surgical planning. 1

Do not delay imaging or referral—chronic tears (>3-4 weeks) require more complex reconstruction rather than primary repair, with inferior outcomes. 2, 3

Do not assume this is a non-urgent injury—while not limb-threatening, the narrow window for optimal surgical repair makes this time-sensitive. 1, 2

Do not confuse with lateral/medial epicondylitis—those are chronic overuse injuries without acute traumatic mechanisms or "tear" sensations. 2, 5

Injury Pattern Considerations

Traumatic ruptures (like this case) have significantly higher association with short head involvement compared to atraumatic ruptures. 1

• Partial rupture with intact short head is the most common overall pattern 1
• However, the acute traumatic mechanism here increases likelihood of complete rupture involving both heads 1