What is the differential diagnosis and appropriate workup for lateral elbow pain, suggestive of tennis elbow?

Differential Diagnosis and Workup for Lateral Elbow Pain (Tennis Elbow)

Differential Diagnosis by Anatomic Location

For lateral elbow pain suggestive of tennis elbow, the primary diagnosis is lateral epicondylitis (tendinosis of the common extensor tendon, particularly the extensor carpi radialis brevis), but you must systematically exclude other anatomically distinct pathologies in this region. 1

Lateral Elbow Pathologies:

• Lateral epicondylitis (tennis elbow): Degenerative tendinopathy of the common extensor origin at the lateral epicondyle, most commonly affecting the extensor carpi radialis brevis tendon 2, 3
• Posterior interosseous nerve syndrome (supinator tunnel syndrome): Entrapment of the deep branch of the radial nerve as it passes through the supinator muscle—a critical differential that mimics therapy-resistant lateral epicondylitis 4
• Radial tunnel syndrome: Compression of the radial nerve proximal to the supinator muscle 5
• Osteochondral lesions: Capitellum or radial head pathology 1
• Intra-articular bodies: Loose bodies causing mechanical symptoms 1
• Radiocapitellar arthritis: Degenerative changes at the radiocapitellar joint 1

Other Elbow Pathologies to Consider:

• Medial epicondylitis (golfer's elbow): Common flexor tendon tendinosis at the medial epicondyle 1
• Biceps tendinopathy: Distal biceps tendon pathology 1
• Collateral ligament tears: Ulnar or radial collateral ligament injury 1
• Cubital tunnel syndrome: Ulnar nerve compression at the medial elbow 1
• Occult fracture or stress fracture: Particularly in the setting of acute-on-chronic pain 1

Clinical Diagnosis

The diagnosis of lateral epicondylitis is primarily clinical and does not require imaging in typical presentations. 2

Key Clinical Features:

• Pain localized to the lateral epicondyle that worsens with activity 2, 3
• Pain with resisted wrist extension (most specific provocative test) 2
• Pain with resisted middle finger extension (Maudsley's test) 3
• Weakened grip strength on the affected side 3
• Age typically >40 years, affecting dominant arm in 75% of cases 2
• History of repetitive wrist extension, radial deviation, and forearm supination (occupational or athletic) 2, 3

Red Flags Suggesting Alternative Diagnosis:

• Neurologic symptoms (numbness, tingling, weakness in radial nerve distribution) suggest posterior interosseous nerve syndrome 4
• Night pain or pain at rest suggests inflammatory or neoplastic process 1
• Mechanical symptoms (locking, catching) suggest intra-articular pathology 1
• Medial-sided pain points to medial epicondylitis or cubital tunnel syndrome 1, 6

Appropriate Workup

Initial Imaging:

Plain radiographs of the elbow are the most appropriate initial imaging study and should be obtained in all patients to rule out osseous pathology, even when lateral epicondylitis is clinically suspected. 1, 2

• Standard elbow radiographs (AP, lateral, and oblique views) can identify:
  • Intra-articular bodies 1
  • Heterotopic ossification 1
  • Osteochondral lesions 1
  • Soft tissue calcification 1
  • Occult fractures 1
  • Osteoarthritis 1
• Comparison views of the contralateral elbow are often useful 1

Advanced Imaging (When Indicated):

MRI or ultrasound should be considered only if radiographs are normal or nonspecific AND there is clinical suspicion for tendon tear, nerve entrapment, or other soft tissue pathology. 2

• MRI of the elbow is indicated when: 1

  • Symptoms persist despite 6-12 weeks of conservative treatment
  • Clinical examination suggests tendon tear or significant degeneration
  • Suspicion for posterior interosseous nerve syndrome or other nerve pathology
  • Concern for intra-articular pathology not visible on radiographs

• Ultrasound can assess tendon degeneration and vascularity but does not reliably predict clinical outcomes 7

Electrodiagnostic Studies:

Electromyography (EMG) and nerve conduction studies should be obtained when neurologic symptoms suggest posterior interosseous nerve syndrome or radial tunnel syndrome, particularly in therapy-resistant cases. 1, 4

• EMG helps differentiate nerve entrapment from lateral epicondylitis 4
• This is critical because posterior interosseous nerve syndrome can masquerade as refractory tennis elbow 4

Common Pitfalls and Caveats:

• Missing posterior interosseous nerve syndrome: In therapy-resistant lateral elbow pain, always consider nerve entrapment—this requires surgical decompression, not tendon treatment 4
• Overreliance on clinical diagnosis alone: While lateral epicondylitis is primarily clinical, radiographs should still be obtained to avoid missing significant osseous pathology 1
• Premature advanced imaging: MRI is not indicated as initial imaging for typical lateral epicondylitis presentations 1
• Assuming all lateral elbow pain is tennis elbow: The differential is broad, and systematic evaluation prevents unnecessary treatments 1, 5