Fig 1. The reflex hammer at the Achilles tendon
Fig 2. The most well known test of the reflex hammer is at the knee joint
The Achilles reflex test (AKA ankle reflex test) tests for a deep tendon reflex with the use of a reflex hammer (fig 1). This assesses the S1 nerve root, as well as a first-line assessment for neurological deficits. The test is performed with the patient in a relaxed supine position with their knee flexed and hip externally rotated. The Achilles tendon area is exposed from the proximal calf to the foot. One of the examiner’s hands holds the reflex hammer, while the other hand holds the patient’s foot in a slightly dorsiflexed position. With the reflex hammer, strike the Achilles tendon and grade the patient’s response accordingly. Deep tendon reflexes are graded from 0 to 4+: 0 is no response, 1+ is a diminished response, 2+ is normal/average, 3+ is brisker than average, 4+ is very brisk and hyperactive with clonus.
Amanda Figliuzzi; Mohammed A. Al-Dhahir. “Achilles Reflex.” StatPearls [Internet], 2018.