The Achilles tendon, located at the back of the lower leg, plays a significant role in everyday movement. When injuries occur to this important structure, diagnostic tests help healthcare professionals determine the nature and extent of the damage. One such assessment is the Achilles tendon pinch test, also known as the Thompson test, which offers a straightforward way to evaluate the tendon’s integrity.
Understanding the Achilles Tendon
The Achilles tendon, also called the calcaneal tendon, is the thickest and strongest tendon in the human body. It is situated at the back of the lower leg, connecting the calf muscles to the heel bone (calcaneus).
The primary function of the Achilles tendon is to facilitate plantarflexion, which is the action of pointing the foot downward. This movement is fundamental for activities like walking, running, jumping, and standing on tiptoes. The tendon also acts like a spring, storing and releasing energy during activities such as running, which enhances movement efficiency. Its strength and elasticity allow for the transfer of force from the calf muscles to the foot, enabling essential daily movements.
Performing the Pinch Test
The Achilles tendon pinch test is a non-invasive physical examination technique used to assess the integrity of the Achilles tendon. To perform this test, the patient typically lies face down (prone) on an examination table with their feet and ankles hanging freely over the edge. This position allows the feet to be relaxed and unsupported, making any movement more apparent.
The examiner then gently but firmly squeezes the calf muscle of the affected leg. The healthcare provider observes the foot’s movement in response to this squeeze. It is common practice to perform the test on both legs to compare the response of the potentially injured side with the uninjured side.
What Pinch Test Results Indicate
A normal, or “negative,” result occurs when squeezing the calf muscle causes the foot to move downward, or plantarflex. This downward movement indicates that the Achilles tendon is intact and properly transmitting the force from the calf muscles to the heel bone. Such a result suggests that the tendon has not suffered a complete tear.
Conversely, an “abnormal” or “positive” result is indicated by a lack of foot movement or very weak movement when the calf muscle is squeezed. This absence of plantarflexion strongly suggests a complete rupture or tear of the Achilles tendon, as the connection between the calf muscles and the heel bone is interrupted. While the Thompson test is highly accurate, it is considered a strong indicator rather than a definitive diagnosis on its own. False-negative results can occur in rare situations, for example, if other muscles still allow some foot movement.
Complementary Diagnostic Methods
While the Achilles tendon pinch test provides valuable initial information, healthcare professionals often use additional diagnostic tools to confirm an Achilles tendon injury and assess its full extent. A thorough physical examination typically accompanies the pinch test, involving palpation of the tendon to feel for any gaps or defects along its length. The examiner may also assess the patient’s range of motion and ability to bear weight or stand on their toes.
Imaging techniques are frequently employed to provide a clearer picture of the tendon’s condition. Ultrasound is a common method that can show the tendon in real-time, helping to determine if a tear exists and its size. Magnetic Resonance Imaging (MRI) scans offer detailed images of soft tissues, which can confirm the diagnosis of a rupture, determine if it is partial or complete, and pinpoint its exact location. These complementary methods help rule out other conditions and guide appropriate treatment decisions for the best recovery.