What is thompson test?

Thompson Test (Simmonds-Thompson Test)

Introduction

The Thompson Test, also referred to as the Simmonds-Thompson Test, is a widely used orthopedic examination technique designed to assess the integrity of the Achilles tendon. It is especially useful in diagnosing suspected ruptures of the tendon, which are common in active individuals, particularly middle-aged athletes involved in high-impact sports like basketball, tennis, or sprinting. The Achilles tendon, being the thickest and strongest tendon in the human body, plays a vital role in plantarflexion of the foot. A rupture can be debilitating and requires timely identification and intervention. The simplicity and high reliability of the Thompson Test make it an essential part of clinical practice.

Purpose of the Test

The primary goal of the Thompson Test is to determine whether the Achilles tendon has been completely ruptured. A complete rupture typically results from a sudden forceful contraction of the calf muscles during activities like jumping or accelerating from a stationary position. When the tendon is intact, a contraction of the calf muscle group (triceps surae) leads to visible movement—specifically, plantarflexion of the foot. In contrast, if the tendon is completely torn, this movement will be absent, even if the muscle contracts. Thus, the Thompson Test serves as a quick and efficient method to distinguish between an intact, partially torn, or fully ruptured Achilles tendon.

Relevant Anatomy

The Achilles tendon is formed by the merging of two major calf muscles—the gastrocnemius and the soleus—collectively known as the triceps surae. These muscles converge into a single tendon that inserts into the posterior aspect of the calcaneus (heel bone). When the gastrocnemius and soleus muscles contract, they transmit force through the Achilles tendon, pulling the heel upward and causing the foot to point downward (plantarflexion). This mechanism is essential for walking, running, and jumping. If the tendon is ruptured, the link between muscle contraction and foot movement is disrupted.

Test Positioning and Procedure

To perform the Thompson Test, the patient is positioned lying face down (prone) on an examination table with their feet hanging freely over the edge. It is important that the patient’s legs and feet are completely relaxed to avoid any involuntary resistance that may affect the result. The examiner then firmly squeezes the mid-portion of the patient’s calf muscle. In a healthy individual with an intact Achilles tendon, this squeeze will trigger a plantarflexion response in the foot. This occurs as the contraction of the calf muscle transmits force through the tendon to the heel.

In a positive Thompson Test—indicating a ruptured Achilles tendon—the foot does not move upon squeezing the calf. The absence of plantarflexion suggests that the force generated by the muscle contraction is not being transmitted to the foot, most likely due to a complete tear in the tendon. If the movement is weak or minimal, it could indicate a partial tear or degeneration of the tendon tissue.

Interpretation of Results

A normal Thompson Test results in visible plantarflexion of the foot, confirming that the Achilles tendon is intact and capable of transmitting muscle contraction force. A positive result, where no movement occurs, strongly indicates a complete rupture. In some cases, there may be a faint movement due to other nearby muscles like the posterior tibialis or peroneal muscles, but this is typically weak and not as pronounced as the normal plantarflexion seen in a healthy tendon. Therefore, clinical expertise and experience are crucial in interpreting borderline cases.

Reliability and Validity

Several studies have validated the Thompson Test as a highly sensitive and specific clinical tool for diagnosing Achilles tendon ruptures. Sensitivity values have been reported as high as 96 to 100 percent, with specificity ranging from 93 to 100 percent. These values indicate that the test is very reliable when properly conducted and interpreted. However, false negatives can occur, particularly in chronic ruptures or if scar tissue bridges the gap between the torn ends, leading to slight foot movement that might be misinterpreted as a negative result.

Common Errors and Considerations

To ensure accuracy, the test must be performed with proper technique. Common mistakes include failing to position the patient prone, applying pressure to the wrong area of the calf, or not fully relaxing the limb. Additionally, comparing the affected side with the unaffected side is critical to identifying subtle abnormalities. The presence of bruising, swelling, or palpable gaps along the Achilles tendon can also support the diagnosis and should be considered alongside the Thompson Test.

Clinical Significance

The Thompson Test is especially valuable in emergency and sports settings where rapid diagnosis is essential. A confirmed Achilles rupture often requires further imaging—such as ultrasound or MRI—to determine the location and extent of the tear. Based on the findings, treatment options range from conservative management (using a cast or walking boot) to surgical repair, particularly in younger or athletic individuals. Early diagnosis via clinical examination, including the Thompson Test, can significantly improve outcomes and reduce recovery time.

Limitations

Despite its usefulness, the Thompson Test is not foolproof. It may not detect partial ruptures or chronic degenerative changes in the tendon, especially in older adults. Additionally, excessive muscle tightness, obesity, or pain may interfere with test results. Therefore, while the Thompson Test provides immediate clinical insight, it should be supplemented by imaging when uncertainty remains.

Conclusion

The Thompson Test remains a fundamental assessment tool in musculoskeletal and sports medicine. Its ease of use, non-invasive nature, and high diagnostic value make it a go-to examination for suspected Achilles tendon ruptures. When performed correctly and interpreted in the context of patient history and other findings, the Thompson Test plays a key role in prompt diagnosis and management, potentially preventing long-term disability and improving functional outcomes.

References


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