The Thompson Test is a physical examination technique healthcare providers use to evaluate the integrity of the Achilles tendon. This maneuver is performed when a patient reports symptoms suggesting a potential injury to this tendon, such as a sudden “pop” or sharp pain in the back of the ankle. The test offers a rapid, in-office assessment to determine if the connection between the powerful calf muscles and the heel bone has been broken. Understanding the test procedure and what a positive result indicates is the first step in diagnosing a significant lower leg injury.
Performing the Thompson Test
The test requires no specialized equipment, making it a highly accessible diagnostic tool. To begin, the patient is positioned either kneeling on a chair or lying face-down on an examination table, with the feet extending over the edge and the ankle and calf muscles relaxed. This positioning allows the foot to hang freely in a neutral or slightly downward-pointed position.
The examiner then uses their hand to firmly squeeze the bulky part of the calf muscle. These two muscles join together to form the Achilles tendon, which inserts into the heel bone, or calcaneus. In a person with an intact Achilles tendon, this squeeze indirectly pulls on the tendon, causing the foot to automatically move downward, a motion called plantar flexion. Observing this passive movement is the central point of the test.
Understanding the Positive Result
A positive Thompson Test is confirmed when the squeeze of the calf muscle fails to produce any movement or only a minimal downward twitch in the foot. This absence of passive plantar flexion signifies that the functional link between the calf muscle and the foot has been severed. When the muscle belly is compressed, the force generated is not transmitted to the heel bone because the Achilles tendon has ruptured.
The positive result is considered a strong clinical indicator of a complete rupture of the Achilles tendon. The tendon, the thickest and strongest in the body, is unable to transmit the tension from the contracting calf muscles to the foot, which is its normal function. While other small tendons can sometimes allow for a slight degree of active ankle movement even after a rupture, the Thompson Test isolates the primary connection, making its result highly reliable in an acute injury setting. The test has demonstrated high sensitivity and specificity in detecting this type of injury, confirming its value in the initial assessment.
Next Steps After Diagnosis
Following a positive Thompson Test, a healthcare provider confirms the diagnosis and plans the appropriate treatment. While the physical exam provides a compelling indication of a rupture, further medical imaging is often utilized to confirm the extent of the injury. Ultrasound is a common initial imaging choice as it can clearly visualize the soft tissues, confirm the rupture, and measure the size of the gap between the torn tendon ends.
Magnetic Resonance Imaging (MRI) may also be ordered. Once the rupture is confirmed, treatment will be guided by factors such as the patient’s age, activity level, and the severity of the injury. The two primary management paths are non-surgical treatment, which involves resting and immobilizing the leg in a cast or walking boot with the foot pointed down, and surgical repair.
Surgical repair generally involves stitching the torn ends of the tendon back together, which can be done through an open incision or using minimally invasive techniques. Non-surgical management avoids the risks of surgery but may be associated with a slightly higher chance of the tendon rupturing again. Both approaches require a period of immobilization followed by a comprehensive rehabilitation program to restore strength and function to the lower leg.