Thompson test:

The Thompson Test (Simmonds-Thompson Test) is used to assess the integrity of the Achilles tendon by squeezing the calf. It is a quick and reliable clinical test that helps identify a complete rupture of the Achilles tendon, commonly performed in emergency and sports medicine settings where imaging is not immediately available.

Clinical Anatomy

The Achilles tendon is the strongest tendon in the human body, formed by the triceps surae muscle group:

• Gastrocnemius – two heads originating from the femoral condyles

• Soleus – a broad origin from tibia and fibula

• Plantaris – a small accessory muscle, absent in 7–20% of individuals¹

These muscles merge in the distal calf to form the Achilles tendon, inserting onto the calcaneus. Tendons consist of dense collagen fibers, allowing them to withstand extreme loads but also making them vulnerable to rupture, particularly during explosive movements.

Purpose

The test aims to determine whether there is a complete rupture of the Achilles tendon.Partial ruptures are more challenging to detect, as plantarflexion may still occur due to compensatory action from the plantaris and deep toe flexors.

Test Procedure

1. The patient lies prone with the foot hanging freely off the examination table, or with knees flexed at 90°.

2. The examiner squeezes the calf (gastrocnemius-soleus complex).

3. Normal response: The ankle moves into plantarflexion.

4. Positive test: No plantarflexion occurs, suggesting a complete rupture.

Additional clinical signs of rupture:

• The foot rests passively in plantarflexion when relaxed

• A palpable gap 3–6 cm above the calcaneal insertion

• Significantly reduced strength in plantarflexion³ ⁴

Evidence

The test was first described by Simmonds (1957) and popularized by Thompson (1962). It is widely used in acute care because of its simplicity and diagnostic strength⁵.

Diagnostic accuracy:

• Sensitivity: >90%⁶ ⁷

• Specificity: 93%⁶

• Meta-analysis (Wang et al., 2013): Sensitivity 96%, specificity 93% → highly reliable for ruling in and ruling out rupture⁶

This makes the Thompson Test one of the most accurate bedside tools for detecting Achilles tendon rupture.

Limitations

• Less effective for partial ruptures or chronic injuries, as plantarflexion may still occur

• Other muscles (e.g., plantaris, toe flexors) can mask a rupture

• Imaging such as ultrasound or MRI is recommended to confirm diagnosis and guide treatment⁷ ⁸

Mechanism Behind the Test

Research by Scott et al. demonstrated that calf compression creates a bulging effect in tendon tissue, resulting in plantarflexion².Douglas et al. later showed that patients with gastrocnemius rupture but intact soleus could still produce plantarflexion, highlighting that the test should not be used in isolation⁹.

Conclusion

The Thompson Test is a simple, sensitive, and non-invasive method to assess for Achilles tendon rupture.Although highly reliable for complete ruptures, it has limitations in detecting partial or chronic injuries. For the most accurate evaluation, the test should be combined with imaging modalities such as ultrasound or MRI.

Sources:

1. Simpson, S. L., Hertzog, M. S., & Barja, R. H. (1991). The plantaris tendon graft: An ultrasound study. The Journal of Hand Surgery, 16(4), 708–711. Last Assessed 31/10/2024

2.  Thompson, T. Campbell M.D., & Doherty, John H. M.D. (1962). Spontaneous Rupture of Tendon of Achilles: A New Clinical Diagnostic Test. The Journal of Trauma: Injury, Infection, and Critical Care, 2(2), 126-129. Last assessed 31/10/2024

3. Verhaar JAN, van der Linden AJ. Orthopedie. Bohn Stafleu van Loghum, 2008, p. 165-166.

4. Brukner P, Khan K. Clinical Sports Medicine. 3rd ed. McGraw-Hill Book Company, 2010.

5. Davis, S., Lott, A., & Besada, E. (2017). GP-confirmed complete Achilles tendon rupture using pocket-sized ultrasound: a case report. BJGP Open, 1(3), bjgpopen17X100893. Last assessed; 31/10/2024

6. Wang, C., Chen, P., Yang, K., Wang, C., & Chen, I. (2024). Current treatment concepts for Achilles tendon rupture. Tzu Chi Medical Journal, 36(1), 46–52. Last assessed: 31/10/2024

7. Achilles tendon rupture: a challenging diagnosis. (2000, October 1). PubMed. Last assessed: 31/10/2024

8. Neill, E., & Shyy, W. (2023). SONO case series: point-of-care ultrasound for Achilles tendon injury. Emergency Medicine Journal, 40(5), 385–387. Last Assessed; 31/10/2024

9. Douglas J, Kelly M, Blachut P. Clarification of the Simmonds-Thompson test for rupture of an Achilles tendon. Can J Surg. 2009 Jun;52(3):E40-1.