What is the diagnostic approach for a patient with a suspected Achilles tendon injury, considering their age, sex, physical activity level, and past medical history?

Diagnosing Achilles Tendon Injuries

Diagnose Achilles tendon injuries primarily through clinical examination using at least two specific physical tests—the Thompson test, assessment of decreased ankle plantar flexion strength, palpation for a gap or defect in the tendon, and evaluation of increased passive ankle dorsiflexion—without routine imaging in most cases. 1

Clinical History

Obtain specific details about the injury mechanism and symptom pattern:

• For acute ruptures: Ask about sudden onset during activities requiring jumping, running, or quick turns, often described as feeling like being "kicked in the back of the heel" 2
• For tendinopathy: Document insidious onset with chronic posterior heel pain and swelling aggravated by increased activity and pressure from shoes, with relief when walking barefoot (common in insertional tendinitis) 1
• Age-specific patterns: Patients ≤12 years more commonly sustain traumatic injuries (penetrating or blunt trauma), while adolescents ≥14 years typically rupture through forceful muscular contraction 3
• Risk factors: Inquire about prior clubfoot treatment with Achilles tenotomy, which increases rupture risk 3

Physical Examination

Perform at least two of these four specific tests to establish diagnosis with 100% sensitivity: 1, 4

• Thompson/Simonds squeeze test: Squeeze the calf while patient prone with feet hanging off table; absence of plantar flexion indicates complete rupture 1, 5
• Decreased ankle plantar flexion strength: Compare to contralateral side 1
• Palpable gap or defect: Feel along the tendon for discontinuity, typically 2-6 cm proximal to calcaneal insertion 1
• Increased passive ankle dorsiflexion: Compare resting tension and range of motion to uninjured side 1

For tendinopathy, examine for: 1

• Prominence medially and laterally to the Achilles tendon insertion
• Central or global tenderness at the tendon
• Tendon thickening and palpable nodules
• Anatomic deformities: forefoot and heel varus, excessive pes planus, or foot pronation

Important caveat: Excessive swelling and pain can limit examination accuracy up to 48 hours after acute injury, potentially masking the diagnosis; consider re-examination after 3-5 days if initial findings are equivocal 1, 6

Imaging: When and What to Order

Clinical examination alone is sufficient for diagnosis in most cases—imaging should be reserved for specific indications, not routine use. 4

Plain Radiographs

Order radiographs when: 1

• Evaluating for insertional tendinitis to identify spurring or erosion at the Achilles insertion
• Detecting calcific tendinosis or soft-tissue swelling
• Ruling out other bony abnormalities causing symptoms

Advanced Imaging (Ultrasound or MRI)

Reserve for these specific scenarios only: 1, 7

• Diagnosis remains unclear after thorough history and physical examination
• Recalcitrant pain despite adequate conservative management
• Preoperative planning for surgical intervention
• Ambiguous presentations or subacute/chronic injuries 4

Key evidence: Physical examination has 100% sensitivity for complete ruptures, superior to MRI which misread 4 of 66 complete tears as partial and 2 as inconclusive 4. MRI delays diagnosis by an average of 5.1 days and surgical intervention by 6.8 days compared to clinical diagnosis alone 4.

If ordering advanced imaging:

• Ultrasound: First-line choice due to ease of use, ability to view dynamic function, and lower cost; demonstrates tendon thickening, decreased echogenicity, and calcification 7
• MRI: 95% sensitive and 95% specific for chronic degenerative changes, partial tears, and tendon thickening; reserve for complex cases requiring detailed preoperative planning 1, 7

Differential Diagnoses to Consider

Rule out these conditions during evaluation: 1

• Retrocalcaneal bursitis
• Haglund's deformity
• Neurologic causes of heel pain
• Partial versus complete tears (may be difficult to distinguish acutely)

Diagnostic Algorithm Summary

1. Obtain focused history on injury mechanism, symptom pattern, and risk factors
2. Perform at least two specific physical tests (Thompson, strength, gap, dorsiflexion)
3. If all three clinical findings present (abnormal Thompson, decreased resting tension, palpable defect): Diagnose clinically without imaging 4
4. If examination limited by swelling/pain: Re-examine in 3-5 days 6
5. Order plain radiographs only for suspected insertional pathology or bony abnormalities 1
6. Reserve ultrasound/MRI for unclear diagnosis, failed conservative treatment, or preoperative planning 1, 4