Reflexes are involuntary contractions of muscles in response to a stimulus and are classified as deep tendon, superficial, or pathologic (Hinkle, 2021). The most common reflexes tested are the deep tendon reflexes which include the biceps, triceps, brachioradialis, quadriceps (patellar), and Achilles (ankle). When testing deep tendon reflexes, ensure your patient is completely relaxed as these reflexes can be a challenge to elicit when the muscles are tense. Holding the handle of a reflex hammer loosely between your thumb and index finger, relax your wrist, and strike the tendon briskly with the head of the hammer using a rapid wrist movement. Let the hammer do the work and strike the tendons in the following areas (Gelb, 2022):
*Refer to our Neurologic Assessment Pocket Card for details on eliciting the deep tendon reflexes.
- Biceps reflex – just anterior to the elbow
- Triceps reflex – just posterior to the elbow
- Brachioradialis reflex – about 2 to 4 inches above the wrist on the radial aspect of the forearm
- Quadriceps (patellar) reflex – just below the patella
- Achilles (ankle) reflex – just behind the ankle
Scale for Grading Deep Tendon Reflexes (Bickley et al., 2021)
Note the speed, force, and amplitude of the reflex response and grade the response using the following 0 to 4 scale. Always compare the response of one side with the other.
4 = Very brisk, with clonus (rhythmic oscillations between flexion and extension)
3 = Brisker than average; possibly but not necessarily indicative of disease (hyperactive)
2 = Average; normal
1 = Somewhat diminished, or requires reinforcement (hypoactive)
0 = Reflex absent
Results can be recorded as a fraction that indicates the scale range, such as 2/4 (2 on a scale of 4). Scale ratings can be subjective, therefore some clinicians may choose to use the terms present
, and diminished
. The response partly depends on the force of the strike on the tendon, but you should only use enough force to elicit a definite reponse. Increased, decreased, or even absent reflexes that are observed symmetrically may be normal. Hyperactive reflexes may indicate a central nervous system (CNS) lesion affecting the descending corticospinal tract. Check for additional motor findings such as weakness, spasticity, and/or a positive Babinski sign. Hypoactive or absent reflexes may indicate peripheral nervous system (PNS) lesions affecting the spinal nerve roots, brachial or lumbosacral plexus, or peripheral nerves. Check for additional lower motor neuron findings such as weakness, atrophy, and/or fasciculations. (Bickley et al., 2021)
If a reflex is reduced or absent, try using reinforcement to increase reflex activity. Reinforcement involves isometric contraction of other muscles for up to 10 seconds that can increase reflex activity. For example, to reinforce the arm reflexes, ask the patient to clench the teeth or to squeeze both knees together. If the leg reflexes are decreased or absent, have the patient lock their fingers together and pull one hand against the other. Ask the patient to pull just before you strike the patella or Achilles tendon (Bickley et al., 2021).
Interpreting Deep Tendon Reflexes (Gelb, 2022)
While it is important to grade the reflexes, comparing reflexes on one side of the body to another is even more critical. The most essential comparison is between right and left, where asymmetry may be significant. As you perform your assessment, test the reflexes on one side immediately after testing the corresponding reflex on the other side, instead of testing all reflexes in one limb and then testing the other limb. If reflexes are brisk, it may be difficult to detect asymmetry. Try to lighten the stimulus until it just barely elicits a response. Check for and document the following (Gelb, 2022):
- Is the threshold stimulus the same on each side, or do you need to hit harder on one side than the other?
- If the threshold stimulus is the same on each side, does it elicit the same level of response on each side?
- Ensure the joint is fully relaxed at a 90 degree bend.
- Strike the joint only with enough force to elicit a response.
- If a reflex is reduced or absent , try using reinforcement to increase reflex activity.
- Check for asymmetry in reflex responses between the right and left sides of the body.
Bickley, L. S., Szilagyi, P. G., Hoffman, R. M., & Soriano, R. P. (2021). Bate’s Guide to Physical Examination and History Taking (13th ed.). Wolters Kluwer Health: Philadelphia.
Gelb, D. (2022, July 1). The detailed neurologic examination in adults. UpToDate. https://www.uptodate.com/contents/the-detailed-neurologic-examination-in-adults
Hinkle, J. (2021). Brunner & Suddarth’s Textbook of Medical-Surgical Nursing (15th ed.). Wolters Kluwer Health. https://wolterskluwer.vitalsource.com/books/9781975161057