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Quizzes > Health & Medicine > Human Anatomy & Medicine

Test Your Patellar Reflex Knowledge with This Quiz

Think you can ace the reflex action of knee jerk? Dive into the knee reflex test now!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Illustration for a Patellar Reflex Test quiz featuring knee reflexes on a dark blue background

Use this Patellar Reflex Test quiz to practice the knee‑jerk exam and see what each response means. You'll review technique, grading, and nerve roots, spot weak areas before a lab or exam, and, if you want more, study knee anatomy or try more practice questions .

What is the anatomical term for the kneecap?
Fibula
Tibia
Patella
Femur
The kneecap is anatomically called the patella, a flat, triangular bone that covers and protects the front of the knee joint. The patella also increases the leverage of the quadriceps muscle during knee extension. Its name derives from Latin, meaning 'small pan.'
The patellar reflex primarily assesses which spinal cord segments?
L4-L5
L1-L2
S1-S2
L3-L4
The patellar or knee-jerk reflex is mediated by sensory and motor fibers that enter and exit the spinal cord at the L3 and L4 levels. Testing this reflex helps assess the integrity of those segments and the associated femoral nerve.
Which muscle group contains the muscle that is stretched to elicit the patellar reflex?
Hamstrings
Gastrocnemius
Quadriceps femoris
Tibialis anterior
When the patellar tendon is tapped, it stretches the quadriceps femoris muscle group, primarily the rectus femoris. This stretch is detected by muscle spindle receptors, initiating the reflex contraction.
What is the primary purpose of performing the patellar tendon reflex test?
Measure muscle strength
Evaluate joint stability
Test skin sensation
Assess reflex arc integrity
The patellar reflex test evaluates the integrity of the sensory and motor pathways in the reflex arc at the level of the L3-L4 spinal segments. It is not designed to measure overall muscle strength, skin sensation, or joint stability.
Which receptor serves as the afferent component in the patellar reflex arc?
Ruffini ending
Golgi tendon organ
Pacinian corpuscle
Muscle spindle
Muscle spindle fibers in the quadriceps detect the sudden stretch from the tendon tap and send afferent impulses to the spinal cord. Golgi tendon organs, in contrast, sense tension but are not the primary afferent for deep tendon reflexes.
Hyperreflexia of the patellar reflex is most suggestive of which condition?
Upper motor neuron lesion
Neuromuscular junction disorder
Lower motor neuron lesion
Primary muscle disease
Loss of inhibitory descending input from upper motor neurons leads to exaggerated reflex responses, known as hyperreflexia. Lower motor neuron lesions, neuromuscular junction disorders, and primary muscle diseases usually result in diminished or absent reflexes.
Diminished or absent patellar reflex is termed what?
Clonus
Hyporeflexia
Ataxia
Hyperreflexia
Hyporeflexia refers to a reduced deep tendon reflex response, and areflexia indicates a complete absence. These findings often point to peripheral nerve or lower motor neuron pathology.
Through which root do the sensory neurons of the patellar reflex arc enter the spinal cord?
Ventral horn
Ventral root
Dorsal horn
Dorsal root
Sensory (afferent) fibers enter the spinal cord via the dorsal roots and then synapse in the dorsal horn or directly on motor neurons. Motor (efferent) fibers exit via the ventral roots.
During the patellar reflex test, the tendon is tapped just below which anatomical landmark?
Medial malleolus
Fibular head
Lateral femoral epicondyle
Tibial tuberosity
The patellar tendon attaches to the tibial tuberosity, so tapping just below the patella at this point stretches the quadriceps tendon and elicits the reflex. Other landmarks are not involved in this test.
Which neurotransmitter is released by the motor neuron at the neuromuscular junction to trigger quadriceps contraction?
Dopamine
Glutamate
GABA
Acetylcholine
Motor neurons release acetylcholine into the neuromuscular junction, which binds to nicotinic receptors on the muscle fiber, causing depolarization and contraction. Other neurotransmitters serve different functions in the nervous system.
Which descending pathway provides modulatory control of the patellar reflex?
Spinothalamic tract
Dorsal column
Vestibulospinal tract
Corticospinal tract
The corticospinal tract carries motor signals from the brain and exerts inhibitory and facilitatory control on spinal reflex circuits, including the patellar reflex. The spinothalamic and dorsal column tracts carry sensory information, while the vestibulospinal tract modulates posture.
How does long-standing diabetes mellitus most commonly affect the patellar reflex?
Hyporeflexia due to peripheral neuropathy
No change in reflex response
Hyperreflexia due to central lesion
Flaccid paralysis from muscle rupture
Chronic high blood glucose levels in diabetes can damage peripheral nerves, resulting in reduced or absent deep tendon reflexes, including the patellar reflex. This peripheral neuropathy is a common complication of diabetes.
Which medication is known to reduce the amplitude of the patellar reflex by enhancing inhibitory neurotransmission?
Penicillin
Acetaminophen
Diazepam
Insulin
Diazepam, a benzodiazepine, potentiates GABAergic inhibition in the central nervous system, which can reduce spinal reflex excitability and diminish the patellar tendon reflex. Other listed drugs do not have this effect.
In acute spinal cord transection, what is the typical evolution of the patellar reflex?
Immediate hyperreflexia
Immediate clonus without change
Absent initially, then hyperreflexia later
Persistent areflexia
Following acute spinal cord injury, there is an initial phase of spinal shock during which reflexes are lost. Over days to weeks, reflexes return and often become exaggerated (hyperreflexia) as descending inhibition remains impaired.
An asymmetry in patellar reflex latency greater than how many milliseconds between sides is generally considered abnormal?
20 ms
2 ms
10 ms
5 ms
Normal side-to-side latency difference in the patellar tendon reflex is typically within 5 milliseconds. A greater delay may indicate peripheral nerve conduction slowing or a root lesion. Precise measurement requires electrophysiological testing.
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Study Outcomes

  1. Understand physiological principles -

    Grasp the reflex action of knee jerk by learning how the patellar reflex test stimulates spinal cord pathways and involves the quadriceps muscle and femoral nerve.

  2. Demonstrate proper technique -

    Master the step-by-step reflex test on knee method, including patient positioning and percussion techniques for accurate knee jerk assessment.

  3. Analyze reaction variations -

    Identify and differentiate normal, hypoactive, and hyperactive responses in the knee jerk reaction test for more informed clinical judgments.

  4. Apply testing procedures -

    Implement best practices for testing knee reflexes in diverse patient scenarios to enhance diagnostic accuracy and patient comfort.

  5. Interpret assessment results -

    Use quiz insights to evaluate and refine your approach to the patellar reflex test, improving your ability to detect neurological issues.

Cheat Sheet

  1. Anatomy of the Patellar Reflex Circuit -

    The patellar reflex test relies on Ia afferent fibers from muscle spindles in the quadriceps that synapse directly in the spinal cord's ventral horn, eliciting a monosynaptic contraction. This reflex action of knee jerk demonstrates the integrity of spinal segments L2 - L4 and highlights the simplicity of a classic reflex arc. Remember "1 afferent, 1 synapse, 1 efferent" as a mnemonic to recall the pathway.

  2. Optimal Technique for a Reflex Test on Knee -

    During testing, the patient should sit with legs dangling and quadriceps relaxed, while the examiner strikes the patellar tendon just below the kneecap using a reflex hammer. Proper alignment and a firm, brisk tap ensure consistent results in your knee jerk reaction test. Use the mnemonic "Relax, Align, Strike" to recall each step for clear and reliable responses.

  3. Grading Scale for Knee Jerk Reaction Test -

    Responses are scored on a 0 to 4+ scale, where 2+ is considered normal; 0 indicates absent reflex, and 4+ signifies hyperreflexia with clonus according to standard neurology guidelines. This standardized grading supports objective assessment when testing knee reflexes across diverse clinical settings. Refer to NIH clinical assessment protocols for detailed scoring charts.

  4. Clinical Insights from Reflex Action of Knee Jerk -

    Hyporeflexia in the patellar reflex can suggest peripheral neuropathy or LMN lesions, while hyperreflexia often points to upper motor neuron issues such as spinal cord compression. Recognizing these patterns during the patellar reflex test helps narrow differential diagnoses efficiently. A handy phrase is "HYPO - NEURO, HYPER - UP" to recall low reflex with peripheral causes and high reflex with central lesions.

  5. Pitfalls and Best Practices in Testing Knee Reflexes -

    Common errors include improper hammer placement or patient muscle tension, which can lead to false-negative or inconsistent responses. To enhance subtle reflexes, gently distract the patient or employ the Jendrassik maneuver, clenching the hands to augment knee responses. Always compare bilaterally and document findings immediately for accurate neurologic records.

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