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9.2: Reflex Tests

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    124982

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    Knee-Jerk (Patellar) Reflex Test

    The knee-jerk (patellar) reflex tests the femoral nerve. View the video showing an example of the patellar reflex test.

    1. Allow the subject to sit comfortably with their legs hanging. Their feet should NOT touch the ground.
    2. Strike the ligament portion of the patellar tendon just below the patella (kneecap) and observe the resulting contraction of the quadriceps muscles and extension of the lower leg.
    patellarreflex_new.png
    Figure \(\PageIndex{1}\) The Patellar Reflex. (Image credit: "Русский" by Вера Милова; Лида Милова, licensed under CC0 1.0, via wikimedia commons) / Labels by Harmony Folse

    Ankle-Jerk Reflex

    The ankle-jerk reflex tests nerves within the sacral plexus. View the video showing an example of the ankle-jerk reflex.

    1. Have the subject sit comfortably on the table with his or her legs free over the edge.
    2. With the shoe off, hold and push the subject’s foot upward slightly then strike the Achilles (calcaneal) tendon (Figure \(\PageIndex{2}\)) at the level of the ankle and observe the resulting plantar flexion of the foot. Plantar flexion is seen as a downward movement of the foot, as occurs when a person points their toes.

    An anatomical illustration of the lower leg, labeling muscles and tendons, including the soleus and peroneus tendons.

    Figure \(\PageIndex{2}\) Achilles (calcaneal) tendon: The red square indicates the region of the achilles tendon that should be struck with the mallet to conduct the ankle-jerk reflex test. (Image credit: Grey's Anatomy by Henry Gray is public domain CC0 1.0) / Red square added by Harmony Folse

    Biceps-Jerk Reflex

    The biceps-jerk reflex will test nerves of the brachial plexus. View the video showing an example of the biceps-jerk reflex.

    1. Have the subject sit comfortably on the table with the arm relaxed and fully extended.
    2. Gently press the biceps tendon in the antecubital fossa with the thumb and strike the thumb with the mallet.
    3. If this procedure is performed correctly, the biceps muscle will shorten and should produce a slight flexion of the forearm.
    A person is using a tool to puncture or inject a small item into the arm of another person.
    Figure \(\PageIndex{3}\) Biceps-Jerk Reflex: Observe the position of the arm and the mallet to conduct the biceps-jerk reflex test. (Image by Harmony Folse, licensed under CC BY-SA 4.0)

    Triceps-Jerk Reflex

    The triceps-jerk reflex will test nerves of the brachial plexus. View the video showing an example of the triceps-jerk reflex.

    1. Have the subject sit comfortably on the table with the arm relaxed and abducted (Figure \(\PageIndex{4}\))
    2. Strike the triceps tendon about 2 inches above the elbow. If there is no response, repeat this procedure, striking to either side of the original point.
    3. If this procedure is performed correctly, the triceps muscle will shorten and should produce a slight extension of the forearm.
    A historical illustration of a young man seated, preparing to receive a vaccination with an administering hand visible.
    Figure \(\PageIndex{4}\) Triceps-Jerk Reflex: Observe the position of the arm and the mallet to conduct the triceps-jerk reflex test. (Image credit: "Textbook of nervous diseases" by Dana, Charles Loomis is public domain CC0 1.0)

    This page titled 9.2: Reflex Tests was last modified on Wed, 03 Dec 2025 22:50:56 GMT and is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Harmony Folse.