Thompson Test in Diagnosing Achilles Tendon Injuries
The Thompson test (also known as Simonds squeeze test) is a critical diagnostic tool for identifying Achilles tendon ruptures, with high sensitivity and specificity as part of a comprehensive clinical examination protocol. 1
Purpose and Technique
The Thompson test serves as one of the primary clinical tests for diagnosing Achilles tendon ruptures. It involves:
- Patient positioning: Prone position with feet hanging over the edge of the examination table
- Technique: The examiner squeezes the calf muscle
- Positive result: Absence of plantar flexion of the foot indicates a complete rupture
- Negative result: Normal plantar flexion indicates an intact tendon
Diagnostic Accuracy and Protocol
The American Academy of Orthopaedic Surgeons recommends performing at least two of the following tests to establish the diagnosis of acute Achilles tendon rupture 2:
- Thompson/Simonds squeeze test
- Assessment of decreased ankle plantar flexion strength
- Presence of a palpable gap (defect or loss of contour)
- Increased passive ankle dorsiflexion with gentle manipulation
This combination approach yields sensitivity values ranging from 73% to 84% and specificity values from 77% to 78% 1.
Clinical Context
The Thompson test is particularly valuable because:
- It is pathognomonic when positive 3
- It can be performed immediately at the point of care
- It helps differentiate complete from partial tears
- It guides treatment decisions between surgical and non-surgical management
Common Pitfalls and Limitations
False negatives may occur in cases of:
- Partial tears
- Significant hematoma formation obscuring clinical findings 4
- Plantaris tendon remaining intact
The definitive benchmark for rupture is the inability to perform a single-leg heel raise 4
Complementary Diagnostic Approaches
When the Thompson test results are equivocal or additional confirmation is needed:
- Ultrasound examination can determine the location of rupture and assess tendon end approximation with 92% accuracy for differentiating full from partial thickness tears 1
- MRI is considered the gold standard with 95% sensitivity and specificity for tendon pathology 1
- Plain radiography should be performed first to identify any associated bony avulsion fractures 1
Integration into Clinical Decision-Making
The Thompson test should be performed in any evaluation of ankle pain to avoid misdiagnosis 5. A positive test, along with other clinical findings, helps guide treatment decisions:
Surgical treatment is typically recommended for:
- Young, active patients
- Athletes seeking return to sports
- Complete ruptures
- Persistent partial ruptures not responding to conservative treatment 1
Non-surgical management is typically recommended for:
- Older, less active patients
- Patients with significant comorbidities
- Tendinopathy without complete rupture 1
The Thompson test remains a cornerstone in the diagnosis of Achilles tendon injuries, providing immediate clinical information that guides further diagnostic and treatment decisions.