The Thompson Test is a straightforward clinical examination used by healthcare professionals to assess the integrity of the Achilles tendon. It serves as a primary diagnostic tool to determine if a complete rupture, or tear, of this tendon has occurred. This method, sometimes referred to as the calf squeeze test, provides a quick and accessible way to assess the Achilles tendon without specialized equipment.
Identifying an Achilles Tendon Rupture
The Achilles tendon, located at the back of the lower leg, is the body’s thickest and strongest tendon, connecting the calf muscles to the heel bone. Its primary function is to facilitate plantarflexion, the downward movement of the foot, enabling activities like walking, running, and jumping. A rupture typically happens due to sudden, forceful contractions or stresses on the tendon, often during dynamic activities such as pushing off while running or jumping. Prompt diagnosis using tests like the Thompson Test is important because delaying treatment for an Achilles tendon rupture can lead to chronic dysfunction and affect long-term recovery.
Performing the Test
To perform the Thompson Test, the patient typically lies face down in a prone position with their feet extending over the edge of an examination table, allowing the ankles to hang freely. The examiner then gently but firmly squeezes the patient’s calf muscles, specifically the gastrocnemius-soleus complex, with their hand. The healthcare professional observes the movement of the patient’s foot during this action.
Understanding the Results
When the calf muscles are squeezed during the Thompson Test, a normal, intact Achilles tendon will cause the foot to involuntarily plantarflex, or point downward. This movement indicates that the connection between the calf muscles and the heel bone is functioning properly. Conversely, a positive result for an Achilles tendon rupture is indicated by the absence or significant reduction of this plantarflexion movement. This lack of movement suggests that the tendon is no longer intact and cannot transmit the force from the calf muscle contraction to the foot. Other, smaller muscles can sometimes still cause some degree of foot movement, even with a ruptured Achilles tendon.
Clinical Context and Accuracy
The Thompson Test is recognized for its diagnostic value in identifying complete Achilles tendon ruptures. Studies indicate it has high sensitivity, often ranging from 96% to 100%, and high specificity, typically between 93% and 100%, making it a reliable initial assessment tool. However, the test primarily detects complete ruptures and may not reliably distinguish between a partial tear and an intact tendon. Due to these considerations, healthcare providers often combine the Thompson Test with other physical examination findings and may order imaging techniques, such as ultrasound or MRI, to confirm the diagnosis and determine the extent of the injury.