Diagnostics Related to the Muscular System Video

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  • 00:00 Knee-Jerk
  • 00:20 Deep Tendon Reflex & ROM
  • 1:40 Electro(neuro)myography
  • 3:32 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
Have you ever wondered how doctors diagnose muscular problems? They have a wide range of tests they can conduct, including deep tendon reflexes, ROM, and electro(neuro)myography.


Remember when you went to the doctor's office and had part of your knee hit with a reflex hammer? Do you recall what happened? Your leg moved a little bit, didn't it? The knee-jerk, or patellar reflex, as it's more correctly called, is just one kind of diagnostic test associated with the muscular system. We'll define it and others now.

Deep Tendon Reflex & ROM

The patellar reflex is a kind of deep tendon reflex, a brisk contraction of a muscle in response to a stretching force. Absence of such a reflex or its diminished response may indicate an abnormality or injury to the muscle, the tendon that connects the muscle to bone, or a part of the nervous system responsible for this reflex. A hyperactive reflex may indicate nervous system disease. And in general, abnormal deep tendon reflexes may be part of a metabolic or endocrine disorder.

So, your doctor isn't just tapping your knee with a hammer for fun! He or she is actually looking for a clue of a deeper problem indicated by whether the reflex is hypo-reflexive or hyper-reflexive, a reflex with a diminished response or an exaggerated response, respectively.

And if your doctor also asks you to lie down so they can move your leg or arm about, again, they're not doing this for the fun of putting your appendages in weird positions. One of the reasons they do this is to check for signs of pain, and another big reason is range of motion (ROM) testing, a diagnostic procedure that evaluates a joint's mobility and muscle strength. Range of motion exercises are also used to increase a person's flexibility, mobility, and strength.


Range of motion tests and deep tendon reflexes are two tests that can be performed by a doctor without any special machines. So let's go over a couple of fancier tests to show you the wide range of things doctors have at their disposal to diagnose muscular system problems.

One such test is electromyography (EMG), the recording, study, and testing of electrical activity produced by muscles. The word comes from 'electro-,' implying electricity or an electric signal; 'myo-,' which means muscle; and '-graphy,' which means recording. The recording generates a record called an electromyogram, where '-gram' means a record or something that's written or drawn.

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