Clinical Signs of Achilles Tendon Rupture
Diagnose acute Achilles tendon rupture by performing two or more of the following clinical tests: Thompson test (calf squeeze test), palpation for a tendon gap, assessment of decreased plantar flexion strength, and evaluation for increased passive ankle dorsiflexion. 1
Key Clinical Findings
The AAOS guideline provides a consensus-based diagnostic approach emphasizing that clinical examination alone is sufficient for diagnosis. The four cardinal signs are:
1. Thompson Test (Simonds Squeeze Test)
- Most commonly performed and reported sign 2
- Squeeze the calf with patient prone; absence of plantar flexion indicates rupture
- Sensitivity reported at 89.8% in clinical practice 2
2. Palpable Gap (Tendon Defect)
- Loss of normal tendon contour
- Typically located 2-5 cm proximal to the calcaneal insertion 2
- Important caveat: May be difficult to detect if significant swelling/edema is present 3
3. Decreased Ankle Plantar Flexion Strength
- Patient unable to perform single-leg heel raise
- Inability to stand or walk on toes 3
- Restricted walking ability is a common presenting complaint 4
4. Increased Passive Ankle Dorsiflexion (Matles Test)
- With gentle manipulation, the affected ankle demonstrates increased dorsiflexion compared to the uninjured side
- Reflects loss of tendon continuity
Clinical Presentation Pattern
Typical history includes:
- Sudden "pop" sensation or feeling "something go" 5
- Whiplash or dagger thrust-like pain at the moment of injury 4
- Sudden pain reported in 95.9% of cases 2
Common pitfall: The diagnosis is frequently missed in sedentary older patients where the injury may be dismissed as an ankle sprain, or when unilateral leg edema leads to suspicion of DVT rather than tendon rupture 3, 5. The presence of all three clinical signs (Thompson test, palpable gap, decreased strength) provides diagnostic certainty 6.
Imaging Considerations
Routine imaging is NOT required for diagnosis 1. The AAOS guideline explicitly states they are unable to recommend for or against routine use of MRI, ultrasonography, or radiography to confirm the diagnosis, as the clinical examination is sufficient 1. However, ultrasound may be useful for surgical planning and to exclude concomitant DVT when swelling is prominent 5.
Diagnostic Algorithm
- Obtain history: sudden pain, "pop" sensation, mechanism of injury
- Perform physical examination: Use at least 2 of the 4 clinical tests above
- If 2+ tests positive: Diagnosis confirmed clinically
- Imaging: Reserve for surgical planning or when diagnosis remains uncertain despite examination
The strength of this recommendation is consensus-based (Level V evidence), but represents the standard of care endorsed by the AAOS 1. The clinical diagnosis should not be delayed awaiting imaging studies.