Thompson's Test (Simmonds Test): Complete Achilles Tendon Rupture Guide
In short
A complete Achilles tendon rupture is frequently misdiagnosed as an ankle sprain. Learn how Thompson calf squeeze test and the Matles test deliver 96 percent sensitivity to detect tendon rupture.
In this guide (8 sections)
Why Up to 25% of Achilles Ruptures are Initially Missed
The Achilles tendon (tendo calcaneus) is the thickest and strongest tendon in the body. Ruptures typically occur in recreational athletes aged 30 to 50 during sudden explosive push-off.
Ruptures are frequently missed because patients can still weakly flex their toes and plantarflex the ankle while non-weight-bearing using accessory muscles (flexor hallucis longus, tibialis posterior, and peroneals). Thompson test bypasses these accessory muscles to evaluate the triceps surae exclusively.
How to Perform Thompson's Calf Squeeze Test
The patient lies prone with both feet dangling completely relaxed over the edge of the examination plinth:
- Positioning: Ensure the patient calf musculature is fully relaxed with no active ankle guarding.
- Mid-Calf Squeeze: The clinician firmly squeezes the middle-to-upper third of the gastrocnemius muscle belly with both hands from side to side.
- Normal (Intact) Response: In a healthy intact tendon, squeezing the calf causes immediate, visible passive plantarflexion of the foot.
- Positive (Ruptured) Finding: The foot remains completely motionless with zero plantarflexion movement, confirming complete Achilles rupture.
The Matles Test and Palpable Tendon Gap
Matles Test (Knee Flexion Test): With the patient prone, both knees are flexed to 90 degrees. In an intact tendon, resting tension keeps the foot in slight plantarflexion. On the ruptured side, the foot falls into neutral or passive dorsiflexion.
Palpable Gap: Direct palpation along the tendon, usually 2 to 6 cm proximal to the calcaneus, reveals a distinct, tender hollow defect (Hatchet sign).
Diagnostic Performance Table
| Examination Sign | Sensitivity | Specificity | Diagnostic Reliability | |
|---|---|---|---|---|
| Thompson's Squeeze Test | 96 to 98 percent | 93 to 98 percent | Gold-standard clinical examination test | |
| Matles Test | 88 to 97 percent | 85 to 95 percent | Highly sensitive visual test in prone knee flexion | |
| Palpable Tendon Defect | 73 to 83 percent | 90 percent | May be masked by hematoma swelling after 48 hours |
Frequently Asked Questions
Can a patient with a complete Achilles rupture walk into the clinic?
Yes. Patients can often walk flat-footed by dragging the foot, but they cannot perform a single-leg heel raise on the injured side.
Is surgery always required for an Achilles tendon rupture?
No. Modern functional rehabilitation protocols using a rigid walking boot with progressive heel wedges and early weight-bearing achieve re-rupture rates equivalent to surgery without surgical infection risks.
Tendon Degeneration and the Hatchet Defect
Achilles tendon ruptures typically occur in the hypovascular zone 2 to 6 centimetres proximal to the calcaneal insertion. Clinical palpation reveals a distinct depression or step-off (the Hatchet sign) where the retracted tendon stumps have separated. Plantaris muscle tendon sparing can produce weak, deceptive active plantarflexion in non-weight-bearing.
Accelerated Functional Rehabilitation Protocol
Modern conservative management utilizes an equinus walker boot with heel wedges, removing one wedge every 2 weeks. Controlled early weight-bearing with protected active dorsiflexion capped at neutral stimulates collagen cross-linking and yields re-rupture rates below 5 percent, matching surgical outcomes without wound infection risks.
Return to Running and Barefoot Precautions
Patients must regain the ability to complete at least 25 single-leg heel raises with symmetrical calf height before jogging is permitted. Walking barefoot on hard domestic stone or marble floors is strictly restricted during early recovery to prevent catastrophic tendon stretching.
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