Medial Hamstring’s Reflex: L5 Test, Technique & Grading

The medial hamstring reflex, also known as the hamstrings reflex or L5 deep tendon reflex, is a neurological examination used to assess the integrity of the L5 nerve root and its associated reflex pathway. It is particularly valuable when evaluating patients with suspected L5 radiculopathy, lumbar disc herniation, or neurological dysfunction affecting the lower extremities.

Unlike the patellar reflex, which primarily evaluates the L2–L4 nerve roots, and the Achilles reflex, which primarily assesses S1–S2, the medial hamstring reflex provides additional information about L5 nerve root function.

What Is the Medial Hamstring Reflex?

The medial hamstring reflex is a deep tendon reflex elicited by tapping the tendons of the medial hamstring muscles, particularly the semitendinosus and semimembranosus.

The reflex is mediated through the tibial division of the sciatic nerve, with the L5 spinal nerve root making a major contribution. Although these muscles receive contributions from multiple spinal segments, the medial hamstring reflex is primarily associated with L5.

When the tendon is tapped, the resulting muscle stretch activates sensory receptors known as muscle spindles. Sensory signals travel to the spinal cord, triggering a motor response that causes the hamstring muscles to contract.

A normal response consists of a brief contraction of the medial hamstrings, sometimes accompanied by slight knee flexion.

Medial Hamstring Reflex Anatomy and Innervation

What Is the Hamstrings Reflex Used For?

The primary purpose of the medial hamstring reflex test is to help evaluate the neurological integrity of the L5 nerve root.

This examination may be useful in the following clinical situations:

• L5 radiculopathy: A reduced or absent medial hamstring reflex, particularly when asymmetric, may support the suspicion of L5 nerve root involvement.
• Lumbar disc herniation: The reflex may contribute to identifying neurological dysfunction associated with lumbar disc pathology.
• Peripheral neurological assessment: Reflex testing helps evaluate the integrity of sensory and motor components of the reflex arc.
• Differential diagnosis: Comparing the medial hamstring, patellar, and Achilles reflexes helps clinicians assess the distribution of neurological abnormalities.

A study published in Surgical Neurology International in 2012 evaluated the diagnostic performance of the medial hamstring reflex in patients undergoing surgery for lumbar disc herniation. The researchers reported that the medial hamstring reflex correctly classified 79% of patients in their study and demonstrated high examiner agreement.

These findings support its clinical usefulness, although reflex testing alone cannot establish a diagnosis of L5 radiculopathy.

How to Perform the Medial Hamstring Reflex Test

Accurate testing requires appropriate patient positioning, identification of the tendon, and careful observation of the resulting muscle contraction.

1. Patient Position

Position the patient prone (lying face down) on an examination table.

• Keep the tested knee slightly flexed.
• Support the lower leg if necessary to promote muscle relaxation.
• Ask the patient to relax the hamstring muscles.
• The patient may look away from the tested side to reduce anticipation of the stimulus.

2. Examiner Position

The examiner stands or sits beside the tested lower extremity.

Place a thumb or finger over the semitendinosus tendon, immediately proximal to the medial knee joint line, on the posteromedial aspect of the knee.

The tendon should be palpated carefully to ensure the reflex hammer stimulates the appropriate structure.

3. Evaluative Procedure

Using a neurological reflex hammer:

1. Maintain gentle contact between the thumb or finger and the semitendinosus tendon.
2. Deliver a quick, controlled tap to the examining finger or thumb with the reflex hammer.
3. Observe and palpate the medial hamstring muscles for a contraction.
4. Look for slight reflexive flexion of the knee.
5. Repeat the examination when necessary.
6. Test the opposite limb and compare the responses.

The examiner should avoid excessive force because a brisk, controlled tap is generally sufficient.

Alternative Testing Position

The reflex can also be examined with the patient seated or lying supine.

The knee is flexed, and the leg is supported. The examiner palpates the medial hamstring tendons near their tibial insertions and taps the fingers positioned over the tendons.

The expected response remains a contraction of the medial hamstring muscles, potentially producing knee flexion.

Medial Hamstring Reflex Grading and Interpretation

The hamstring reflex is evaluated using the standard 0 to 4+ deep tendon reflex grading scale.

A 2+ response is generally considered normal. However, normal reflex intensity varies among individuals, and a symmetric 1+ or 3+ response may also be physiological.

Side-to-side asymmetry is often more clinically significant than the absolute reflex grade.

What Is a Positive Hamstring Reflex Test?

The medial hamstring reflex is not strictly classified as positive or negative. Instead, clinicians determine whether the response is normal, diminished, absent, or exaggerated.

An abnormal finding may include:

• Absent reflex (0): No detectable medial hamstring contraction.
• Reduced reflex (1+): A weak response that may require reinforcement.
• Asymmetric reflexes: A substantial difference between the right and left sides.
• Exaggerated reflexes: An unusually brisk response that requires interpretation alongside other neurological findings.

An absent or diminished reflex may suggest disruption of the peripheral reflex pathway, including potential L5 nerve root dysfunction.

Conversely, increased reflex activity may indicate abnormalities affecting descending motor pathways, particularly when accompanied by spasticity, pathological reflexes, or other upper motor neuron signs.

Clinical Significance in L5 Radiculopathy

The medial hamstring reflex is especially useful because routine neurological examinations often emphasize the patellar and Achilles reflexes, which predominantly assess other lumbar and sacral nerve roots.

In suspected L5 radiculopathy, the examiner should interpret the medial hamstring reflex alongside other clinical findings, including:

• Weakness of great toe extension or ankle dorsiflexion.
• Sensory changes over the dorsum of the foot and great toe.
• Radiating pain into the lower extremity.
• Findings from the straight leg raise test.
• Other lower-limb deep tendon reflexes.

A decreased medial hamstring reflex combined with compatible motor and sensory abnormalities increases clinical suspicion of L5 nerve root dysfunction.

However, a normal medial hamstring reflex does not exclude L5 radiculopathy, and an abnormal response does not independently confirm the diagnosis.

Frequently Asked Questions (FAQ)

1. Which nerve root is tested by the medial hamstring reflex?

The medial hamstring reflex primarily evaluates the L5 nerve root. The muscles involved also receive contributions from S1 and S2, but L5 is the principal segmental level associated with this clinical reflex.

2. Which nerve innervates the medial hamstring reflex?

The reflex is mediated through the tibial division of the sciatic nerve, which supplies the semitendinosus and semimembranosus muscles.

3. What is a normal medial hamstring reflex response?

A normal response involves a brief contraction of the medial hamstring muscles, sometimes producing slight knee flexion. A reflex grade of 2+ is typically documented as normal.

4. What does an absent medial hamstring reflex indicate?

An absent reflex may suggest neurological dysfunction involving the reflex arc, including L5 radiculopathy, peripheral nerve injury, or other lower motor neuron disorders. The finding must be interpreted alongside the complete neurological examination.

5. How is the medial hamstring reflex different from the patellar reflex?

The medial hamstring reflex primarily evaluates L5 nerve root function, while the patellar reflex assesses the L2–L4 spinal segments through the femoral nerve. Both examinations help localize possible neurological abnormalities.

6. Can the medial hamstring reflex diagnose L5 radiculopathy?

No. The medial hamstring reflex is a supportive neurological examination rather than a definitive diagnostic test. Diagnosis requires correlation with symptoms, muscle strength, sensory examination, and imaging or electrodiagnostic testing when clinically indicated.

7. What should the examiner do if the hamstring reflex cannot be elicited?

The examiner should ensure that the patient is relaxed, confirm correct tendon identification, adjust the limb position, and repeat the test. Reinforcement techniques may help elicit a weak response. Findings should always be compared bilaterally.

Conclusion

The medial hamstring reflex test is a useful component of the neurological examination for assessing L5 nerve root function. By tapping the semitendinosus or semimembranosus tendon and observing the resulting muscle contraction, clinicians can assess the integrity of the associated reflex pathway.

Proper positioning, accurate tendon localization, standardized grading, and bilateral comparison improve the clinical value of the examination.

When interpreted alongside motor, sensory, and other reflex findings, the medial hamstring reflex can provide valuable evidence in the evaluation of suspected L5 radiculopathy and lumbar disc disease.

References

1. Orthofixar. Medial Hamstring Reflex: Technique and Use in L5 Radiculopathy.
2. Orthofixar. Deep Tendon Reflex Testing: Grading, Technique and Nerve Root Guide.
3. Esene IN, Meher A, Elzoghby MA, et al. Diagnostic performance of the medial hamstring reflex in L5 radiculopathy. Surgical Neurology International. 2012;3:104. PubMed – PMID: 23087820. DOI: 10.4103/2152-7806.100862.
4. Deep Tendon Reflex: The Tools and Techniques. What Surgical Neurology Residents Should Know. NCBI PubMed Central.
5. Walker HK. Deep Tendon Reflexes. In: Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. NCBI Bookshelf.
6. Physiology, Deep Tendon Reflexes. StatPearls. NCBI Bookshelf.