Deep tendon reflex

Automatic muscle response elicited by tapping a tendon, used to assess particular neural pathways.

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A reflex circuit assessed with a hammer

A deep tendon reflex is a contraction triggered by briefly stretching a muscle through a tap on its tendon. It assesses a circuit involving sensory input, spinal connections and motor output. Knee, ankle, biceps and triceps reflexes provide different information according to the roots and nerves involved.

Reduced responses may accompany some peripheral nerve or root disorders, while very brisk responses may suggest central involvement in the right clinical context. Normal variation also exists. Relaxation, technique and comparison between sides are essential. An isolated absent reflex does not prove compression, and a present reflex does not establish that every aspect of nerve function is normal. Reflexes become more informative when interpreted with strength, sensation and walking findings rather than used as a standalone diagnostic label.

Interpret a finding in context

A clinical finding increases or decreases the plausibility of a diagnosis; it does not replace the full assessment. The clinician compares it with the history, strength, sensation and other relevant observations. An isolated response can be affected by pain, positioning, apprehension or normal variation. Comparison between sides and, when appropriate, between visits is often more informative than a single number. A finding becomes useful when it helps answer a specific clinical question rather than simply adding a label.

How it changes care

The result may lead to activity modification, another investigation, medical referral or continued conservative management. One test should not determine the choice of a therapeutic machine. At TAGMED, findings should help establish a working explanation and measurable goals, followed by review of response to care. Worsening strength or walking requires reassessment. Recent urinary changes or loss of perineal sensation requires emergency evaluation even when another test seems reassuring. Examination also identifies situations in which routine treatment should be postponed. The patient should leave understanding what the finding means, what remains uncertain and what change would require an earlier review.

Frequently asked questions

Is a brisk reflex always abnormal?

No. Symmetry, associated findings and the clinical context determine its significance.

Does a positive test establish a diagnosis?

No; it must be considered alongside the other assessment findings.

Does a normal result rule out every disease?

No. Each test addresses particular functions or diagnostic possibilities.

Must it be repeated at every appointment?

Only when repetition adds useful information for decisions or monitoring.

Does the result select a treatment?

No. Diagnosis, safety, preferences and practical goals remain essential.

Educational information from The Spine Page. This entry does not replace an individual assessment. Documentary version: October 12, 2026. Sylvain Desforges, B.Sc., D.O., N.D., osteopath and naturopath.