Can brisk but symmetrical knee reflexes be a normal variant?

Brisk but Symmetrical Knee Reflexes: Normal Variant Assessment

Brisk but symmetrical knee reflexes can indeed be a normal variant in healthy individuals and do not necessarily indicate pathology when other neurological findings are normal.

Understanding Deep Tendon Reflexes

Deep tendon reflexes (DTRs), including knee reflexes, are typically graded on a scale:

• 0: Absent
• 1+: Diminished
• 2+: Normal
• 3+: Increased/brisk but not necessarily abnormal
• 4+: Very brisk with clonus (abnormal)

Normal vs. Abnormal Reflexes

When evaluating knee reflexes, several factors should be considered:

• Symmetry: Symmetrical reflexes (even if brisk) are generally more reassuring than asymmetrical ones 1
• Associated symptoms: The presence or absence of other neurological signs is crucial
• Patient factors: Age, baseline muscle tone, and anxiety can all influence reflex intensity

Clinical Significance of Brisk Reflexes

Brisk reflexes may be normal in:

• Young, athletic individuals
• Anxious patients during examination
• People with naturally higher muscle tone
• Certain familial patterns

Brisk reflexes become concerning when they are:

• Asymmetrical (suggesting focal pathology)
• Accompanied by other upper motor neuron signs (Babinski sign, clonus)
• Associated with weakness, sensory changes, or coordination problems
• Part of a progressive neurological picture

Differential Considerations

While brisk but symmetrical reflexes can be normal, they may sometimes indicate:

1. Early upper motor neuron disorders: Before other signs develop 1
2. Metabolic conditions: Hyperthyroidism, electrolyte disturbances
3. Medication effects: Certain drugs can enhance reflex responses
4. Parkinson's disease: Research shows increased tendon reflexes can be a feature of Parkinson's disease in some patients 2

Examination Technique Considerations

The technique of eliciting reflexes can significantly influence their appearance:

• Patient positioning and relaxation
• Hammer strike force and location
• Use of reinforcement techniques (Jendrassik maneuver)

When to Investigate Further

Further investigation is warranted when brisk reflexes are accompanied by:

• Progressive changes in reflex intensity
• Development of asymmetry
• New neurological symptoms
• Clonus or pathological reflexes

Conclusion

When evaluating brisk but symmetrical knee reflexes, clinicians should:

1. Consider the complete neurological examination findings
2. Assess for any associated symptoms or signs
3. Document the findings for comparison over time
4. Reassure patients when other neurological findings are normal

Remember that the context of the entire neurological examination is more important than any single finding, including reflex intensity.