Why does a doctor tap your knee?

To test your reflexes, your doctor will use a rubber hammer to tap firmly on the tendon. If certain reflexes are decreased or absent, it will show what nerve might be compressed. Not all nerve roots have a reflex associated with them.

What is the doctor checking when they tap your knee?

The reflex that the doctor checks by tapping your knee is called the patellar, or knee-jerk, reflex. It is also known as a deep tendon reflex (DTR) because the doctor is actually tapping on a tendon called the patellar (say: puh-TEL-ur) tendon.

What does it mean if you have no reflex in your knee?

The normal response is a ‘knee jerk’. This is an example of a reflex, which is an involuntary muscular response elicited by the rubber hammer tapping the associated tendon. When reflex responses are absent this could be a clue that the spinal cord, nerve root, peripheral nerve, or muscle has been damaged.

What happens when your knee was tapped?

The sharp tap on the tendon slightly stretches the quadriceps, the complex of muscles at the front of the upper leg. In reaction these muscles contract, and the contraction tends to straighten the leg in a kicking motion.

What do reflex tests show?

If you think you have brisk reflexes you can ask your doctor for a reflex test. This test helps determine how effective your nervous system is by assessing the reaction between your motor pathways and sensory responses. During the test, your doctor may tap your knees, biceps, fingers, and ankles.

Why do doctors do reflex test?

Why is the knee jerk reflex important for walking?

The primary purpose of the patellar reflex – the stretch reflex of the quadriceps femoris muscle – is to prevent excessive stretching of the quadriceps.

Which nerve is tested by tapping on the patellar ligament?

The patellar reflex, also called the knee reflex or knee-jerk, is a stretch reflex which tests the L2, L3, and L4 segments of the spinal cord.

Why do doctors measure reflexes during a diagnostic exam?

Reflex tests measure the presence and strength of a number of reflexes. In so doing, they help to assess the integrity of the nerve circuits involved.

What does Hyper knee reflexes mean?

Hyperreflexia refers to hyperactive or repeating (clonic) reflexes. These usually indicate an interruption of corticospinal and other descending pathways that influence the reflex arc due to a suprasegmental lesion, that is, a lesion above the level of the spinal reflex pathways.

Why do doctors tap your knee?

The Patellar Reflex Test – Why Doctors Tap Your Knee. When they do this, it causes the muscle spindle in the quadriceps muscle to stretch and that in turn triggers the reflex response to pull the muscle back. This in turn then causes the leg to kick out – just as it does on the leg extension which trains the quadriceps.

What happens to your body when you tap your muscles?

Now, that quick tap should quickly fire your neuromuscular system, causing a rapid stretch of those adjacent muscles and triggering nerve receptors in the tendons. This kicks off a eyeblink-fast nerve impulse transmission up your spinal cord, where it should trigger a reaction to contract the muscle that was just stretched.

What does it mean when your knee jerks a lot?

(1) Hyperactive deep tendon reflex (knee jerks too much): amyotrophic lateral sclerosis, brain tumor, cerebrovascular accident (stroke), hepatic encephalopathy (associated with liver disease), hypocalcemia (low calcium), hypomagnesemia (low magnesium), hypothermia, multiple sclerosis, preeclampsia, spinal cord lesion (e.g., tumor), and tetanus.

How does a doctor test your reflexes?

When the doctor tests your reflexes she’s tapping the tendon that connects the muscle to the bone, which causes the muscle to stretch slightly. This sends a nerve impulse to your spinal cord where it triggers a motor impulse that returns via a parallel nerve and causes the muscle to twitch.