What are the potential non‑traumatic causes of intermittent anterior upper‑arm or para‑elbow pain?

Potential Non-Traumatic Causes of Intermittent Anterior Upper Arm/Para-Elbow Pain

The most common non-traumatic causes of intermittent anterior upper arm and para-elbow pain include biceps tendinopathy, distal biceps tendon tears (partial or complete), lateral antebrachial cutaneous nerve (LACN) compression, medial antebrachial cutaneous nerve (MACN) neuropathy, and less commonly, anterior capsular pathology or referred pain from cervical radiculopathy.

Primary Musculotendinous Causes

Biceps Tendon Pathology

Biceps tendinopathy and tears are the most common sources of anterior elbow pain in non-traumatic presentations 1, 2. The clinical picture typically involves:

• Atraumatic ruptures: 89% involve the long head of the biceps tendon, with the short head remaining intact 1
• Partial tears: More common than complete ruptures, particularly affecting the long head while sparing the short head 1
• Mechanism: Repeated elbow flexion combined with forearm supination and pronation activities 2

The distinction between partial and complete tears matters significantly for surgical planning. MRI demonstrates 92.4% sensitivity and 100% specificity for complete distal biceps tendon ruptures, but only 59.1% sensitivity for partial tears 3. The FABS (flexion-abduction-supination) MRI view can improve visualization of the entire distal biceps tendon on a single image, though recent evidence suggests it changes diagnostic impression in only a minority of cases 1.

Nerve Compression Syndromes

Lateral Antebrachial Cutaneous Nerve (LACN) Compression

LACN compression is an uncommon but frequently misdiagnosed cause of anterior elbow pain 4. Key features include:

• Location: Compression typically occurs at the musculotendinous junction of the distal biceps tendon 4
• Presentation: Anterior elbow pain with clicking, often bilateral, that progressively worsens despite conservative management 4
• Diagnostic challenge: Plain radiography and standard MRI often fail to reveal pathology 4
• Prognosis: Surgical decompression has high success rates with complete symptom resolution in many cases 4

Medial Antebrachial Cutaneous Nerve (MACN) Neuropathy

The anterior branch of MACN can cause medial forearm and anteromedial elbow pain 5. This presents with:

• Trigger: May develop from repeated minor trauma 5
• Symptoms: Pain and dysesthesia in the MACN distribution
• Diagnosis: Electrophysiological studies showing reduced sensory action potential amplitude compared to the contralateral side 5
• Treatment: Responds well to NSAIDs and physical therapy 5

Diagnostic Approach

Initial Evaluation

Start with plain radiographs 3. While often normal in non-traumatic anterior elbow pain, radiographs can identify:

• Soft tissue calcification
• Heterotopic ossification
• Occult fractures
• Osteoarthritis
• Comparison with the contralateral side is valuable 3

Advanced Imaging Selection

When radiographs are normal or nonspecific and soft tissue pathology is suspected, MRI without IV contrast or ultrasound are the appropriate next steps 1.

For suspected biceps tendon pathology:

• MRI is the gold standard with excellent sensitivity and specificity 1, 3
• Ultrasound performs similarly to MRI for complete versus partial tears (95% sensitivity, 71% specificity, 91% accuracy) 3
• Consider FABS view MRI for challenging cases of high-grade partial versus complete tears 1

For suspected nerve compression:

• Standard MRI often fails to identify LACN compression 4
• Electrophysiological studies are essential for confirming MACN neuropathy 5
• High clinical suspicion is required, as these conditions are frequently missed 4, 6

Common Pitfalls

1. Overlooking nerve compression: LACN and MACN neuropathies are uncommon and easily misdiagnosed, potentially leading to permanent neurological damage if untreated 4, 5

2. Assuming all anterior pain is biceps-related: While biceps pathology is most common, failure to consider nerve compression can delay appropriate treatment 2, 6

3. Relying solely on imaging: LACN compression may not be visible on standard imaging, requiring surgical exploration in refractory cases 4

4. Misinterpreting partial tears: MRI has lower sensitivity for partial biceps tears (59.1%) compared to complete tears, and may overestimate triceps tear severity 1, 3

Clinical Decision Algorithm

For intermittent anterior upper arm/para-elbow pain:

1. Obtain detailed history focusing on:

   • Activities involving repetitive elbow flexion with forearm rotation (suggests biceps pathology) 2
   • Presence of clicking or mechanical symptoms 4
   • Distribution of pain and any dysesthesia (suggests nerve involvement) 5

2. Physical examination should assess:

   • Tenderness over biceps tendon insertion
   • Strength testing of elbow flexion and forearm supination
   • Sensory examination in LACN and MACN distributions
   • Provocative maneuvers for nerve compression

3. Begin with plain radiographs 1

4. If radiographs are normal:

   • For suspected tendon pathology: Order MRI without contrast or ultrasound 1
   • For suspected nerve compression: Consider electrophysiological studies 5

5. If conservative management fails after 3-6 months and nerve compression is suspected, surgical exploration may be warranted even with negative imaging 4