How to Perform Physical Assessments at Home

One of the ways that patients can take charge of their own care is to be able to perform basic physical examination tests on themselves. The most basic and easy examination to perform is motor strength assessment. This thread will discuss the nerve roots and muscles involved in testing and testing techniques.

Why Do I Have Muscle Weakness?

During testing, if the muscle tests “weak”, the reason for the weakness has to be identified. Generally there are three reasons for muscle testing weakness; nerve compression, peripheral neuropathy and pain inhibition. Obviously, if you tore a tendon, the muscle would be weak but you probably would not be reading this article as this is not a spine problem.

Each muscle has one or two nerves attached to it. Normally, nerve compression in the lumbar spine (typically from a herniated disc) produces pain, numbness and paresthesias (pins and needles) in the leg. If the compression is more severe, the motor portion of the nerve can be affected. Weakness can develop which is somewhat more serious. Surgical decompression of the root (microdiscectomy) is generally warranted if weakness is present. Timeliness of surgery is important.

For a more thorough understanding of how nerve disorders cause walking abnormalities, see the thread “walking (gait) disorders” on this website.

Pain Inhibition

Pain inhibition will make a muscle test weak even if the nerve connection is perfect. Weakness in this case has to do with the onset of pain interrupting the ability of the brain to contract the muscle. Weakness can occur from both pain inhibition and nerve compression at the same but this coexistence is rare.

With pain inhibition, the greater the force the muscle generates (the greater the contraction), the more intense the pain is noted. Full contraction of the muscle may be excruciating. Patients involuntarily will not fully contract their muscle due to this pain. This is not true weakness as the nerve is most likely intact. If you have significant pain upon testing the muscle and note weakness, the test results if weakness is noted are suspect.

Peripheral Neuropathy

Peripheral neuropathy is a condition noted elsewhere on this website. In this condition, the actual peripheral nerves traveling in the legs (not in the spine) are “sick” and do not communicate with the muscles. Generally, the weakness will be bilateral (on both sides), symmetrical (equal on both sides) and accompanied by “numbness” and “irritability” or hypersensitivity of the feet. The symptoms of peripheral neuropathy do not come on rapidly and weakness from nerve compression is typically unilateral (one sided) so differentiation of this disorder from nerve root compression is relatively easy.

Nerve Compression Motor Strength Weakness

Actual muscle weakness due to nerve compression is a “helpless” type of weakness. No matter how hard you try to contract the muscle, the strength is just not there and the limb collapses under load. Generally, there is no pain except for the “normal” radiation of pain from nerve root compression as noted above. Pain generally does not escalate if the load is increased.

Specific Nerve Roots

S1 Nerve root

The S1 nerve root travels by the L5-S1 disc space before it exits out the spine to travel down the leg. A disc herniation at L5-S1 commonly will compress this root. Pain, numbness and paresthesias will travel down the leg from the buttocks possibly all the way down to the outside of the foot. The main muscle group attached to this nerve is the gastroc-soleus group (the calf muscle).

This group of muscles flexes the foot at the ankle (pushes the foot and toes down). These muscles are extremely strong and give us the ability to “tip toe”. Testing of these muscles is simple. Tiptoe for about 20 feet. Watch your heel on the involved side for any possibility that the muscle starts to fatigue and the heel starts to drop to the ground. The heel does not have to hit the ground (except in severe cases) to demonstrate weakness. If you are unable to keep the heel up and it “gives way” when the toe touches the ground, the muscle has weakness.

If there is any doubt, stand only on the involved leg (lifting the good leg off the ground) and do 20 heels raises in quick succession. There should be no delay or fatigue with lifting this heel. If there is still doubt about the results, repeat this test on the good leg and compare. If there is notable fatigue compared to the good leg, you probably have some motor weakness of the S1 root.

L5 Nerve Root

This nerve root services multiple muscles. The two main muscles are the Tibialis Anterior and the Peroneals. The Tibialis Anterior muscle keeps the foot from slapping on the ground when you take a step and the heel hits the ground. Without the use of this muscle, you can “catch” your foot and stumble when walking. This is called “foot drop”.

Interestingly, the L5 nerve root about 75% of the time supplies the Tibialis Anterior muscle. The other 25% of the time, the L4 nerve root is the main supplier.

The way to test this muscle is to walk on your heels (duck walk). The forefoot and toes should stay off the ground when you do this maneuver. If the foot on the involved side drops somewhat, there is weakness of this nerve.

If there is any doubt, stand only on the involved leg (lifting the good leg off the ground) and do 20 toe raises in quick succession. There should be no delay or fatigue with lifting the forefoot. If there is any doubt about the results, repeat this test on the good leg and compare. If there is notable fatigue compared to the good leg, you probably have some motor weakness of the L5 (or possibly L4) root.

The Peroneals keep the ankle from “turning in” when your heel hits the ground. Weakness of this group of muscles is uncommon even with abject weakness of the Tibialis Anterior. There is no need to test them as patients with weakness feel like they will sprain their ankle simply by walking on uneven ground. If this feeling is not present, the muscles are probably functioning normally. See the walking “gait “ disorders section to better understand these muscles.

L4 Nerve root

This nerve root can supply either the Tibialis Anterior or the Quadriceps Femorus muscles, depending upon the anatomy. Read the Tibialis Anterior testing protocol above in the L5 nerve root section to understand how to test this muscle.

The Quadriceps Femorus muscles (the Quads) are the strong group of muscles found in the anterior thigh above the knee. These muscles straighten the knee. When you take a step and your heel hits the ground, these muscles prevent your knee from buckling.

You must be careful when testing the Quads as if the knee gives way, you can fall to the ground. When you test this muscle, have a hand on a counter to prevent a fall. Just do not put weight on your hand to “help” the muscles unless you feel the Quads about to give way.

Lift up the good leg. Then do a deep squat on the involved leg. Let the knee bend more than 90 degrees. If you can do five of these squats without too much effort, you probably do not have motor weakness. If you get caught in the squat and unable to rise, you probably have weakness.

L3 Nerve Root

This nerve root is generally the main supplier to the Quadriceps Femorus muscles noted above. Testing is discussed under the L4 nerve root discussion.

L1 and L2 Nerve Roots

These nerves generally go to the Psoas muscle group. The Psoas muscles lift the thigh up at the hip. When you step up or ascend stairs, this is the group of muscles that pull up the thigh so the foot can contact the next stair up.

Weakness of these muscles can also be caused by common hip degeneration so the differential of weakness is somewhat more difficult for this self-test.

To test these muscles, there are two home techniques. One is to sit in a chair and simply lift your involved thigh off the seat. Push with your hand to try and force the thigh back onto the seat. Do this several times and compare with your good leg. If you notice a significant difference, there is probable motor weakness present.

The other technique is to lie on your back and lift your straightened leg off the ground 20 times. Compare to your non-involved leg. Weakness should be obvious.

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