Muscle Test Weakness | Nerve Compression

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.

Donald Corenman, MD, DC

Average rating:

81 reviews

Eric S

Sep 26, 2021

by Eric S on Donald Corenman, MD, DC

Successful pars repair at 46 years old

Back in November of 2018 (at 46 years old) I came from Vancouver BC to have a pars repair done with Dr. Donald Corenman at the Steadman Clinic in Vail Colorado. I'm finally posting this review nearly three years later in late 2021. The reason I waited so long was I wanted to know the final result before I posted my review. Unfortunately in that time Dr. Corenman has retired. Nevertheless, I want to post this review of Dr. Corenman and his staff at the Steadman Clinic in their excellent treatment of my L5 pars interarticularis.

I fractured my pars at age 42 back in 2014 when rolling on the gym floor, and was denied treatment by the Canadian healthcare system, probably due to my age. First my GP told me there was no surgical option for a pars defect, which was quite incorrect! I tried to live with it, but the symptoms worsened (periodic random spine slippage and weeks of resultant pain after just bending over to tie my shoe, so I eventually learned to mostly squat and hardly bend). When I finally consulted with Canadian spine surgeons, I was told they believed my pars defect had been congenital (since birth). This was absurd, considering I had done extreme martial arts (including jiu jitsu) for years prior, as well as 5 years of reinforcing steel full time in my 20s, probably the hardest job on the back you can find. No pars defect like mine would possibly have allowed this--ergo it was impossible that I had had the defect since birth. I did however have an asymptomatic congenital spina bifida occulta that made me more susceptible to a pars fracture. In 2014 in one instant, I went from having the strongest back people I knew said they'd ever seen, to being unable to safely bend over and tie my shoe without a non-negligible risk of my spine slipping randomly (which would lead to weeks of pain after each occurrence). This was due to the unilateral L5 pars defect, otherwise known as spondylolysis. It was when lying in pain on the floor 4 years later after maybe the 6th spine slippage event post injury, that I had had enough, and resolved to have surgery. If Canada's "universal health care" said no, I would make lemonade from lemons, and find the very best surgeon in the world at pars repairs. That was Dr. Donald Corenman. Dr. Corenman back in 2018 ran a website https://neckandback.com/ that dedicated many pages to the science of every aspect of pars repairs, from eligibility (good discs on MRI), to best surgical techniques (minimal open compared to minimally invasive), best imaging to use (i.e., O-Arm with Stealth imaging vs. older fluoroscopy), the ideal amount of BMP to use and why not use too much or too little, and much more, all to do with pars repairs, pages upon pages of his site just on the pars, with scientific references and his own extensive expert opinion. As a health research statistician, I was very impressed with this. It was in stark contrast to the websites of other spine surgeons which barely gave the pars a word or two, focusing almost exclusively on fusions. I had found the best surgeon in the world for pars repairs, and so after Dr. Corenman personally screened my MRI to ensure my discs were healthy, I booked the surgery.

Being 46 years old at the time of surgery in 2018, with a 4-year-old pars fracture from 2014 combined with a congenital SBO meant my pars fragment was somewhat atrophied, but it was "very solid", said Dr. Corenman in the operative report. Nevertheless, it was challenging with two things to fix, the pars and SBO, and OR time was around 4 hours. Recovery over the following months was guided by a very clear "Spine binder" from the Steadman Clinic with strict rules of "no BLT" (no bending, lifting or twisting), and illustrated physiotherapy guidelines. They even warned patients to avoid fish oil supplements, which could excessively dampen inflammation and hence slow bone healing. They answered many questions I had during months of recovery, with responses coming from the very supportive Lori Fugate (then director of Dr. Corenman's practice), and Ehrich Bean (then physician's assistant at the practice), as well as a couple calls with Dr. Corenman himself after two of the CT scans. Ehrich Bean offered great advice for taking the spine binder conservatively due to the nature of pars repairs vs. fusions. The final post-op CT scan I had was a couple weeks ago at 34 months post-op, and Dr. Corenman had retired, but I got a very positive and informative call from Eric Strauch (current PA at the Steadman Clinic under Dr. Corenman's replacement there, and who had also worked with Dr. Corenman previously). The staff at the Steadman Clinic were extremely supportive all the way through the process. I should mention, the local Canadian spine surgeon did offer me very good post-operative support including antibiotics as needed to deal with a mild surface incision-site infection early on, booking numerous x-rays when I felt something was amiss, as well as booking all four of my post-op CT scans. I am very grateful for that support also.

My final result shows plenty of solid bone across the pars and a healed SBO, with my vertebral body now a solid bone ring instead of being broken at two places as it was pre-op. Does my spine hold up in the real world? You bet! I have recently dug and moved several yards of dirt and sand and gravel by myself (shovel and wheelbarrow!) to fix our water main, pulled roots from the yard, moved several "portable" (these are HUGE) air conditioners up several flights of stairs my myself, and lifted weights. I now run 2 miles (3.2 KM) several times weekly with a hard 100 meter dash in the middle. I bend deeply before each run I go on, with no spine slippage. My spine feels amazing. I can bend over to do exercise, or real word tasks, with no risk of spine slippage.

My sincere thanks to God, Dr. Donald Corenman, Lori Fugate, Ehrich Bean, Eric Strauch, and the Steadman Clinic, as well as the Canadian spine surgeon who offered me excellent post-operative care back in Canada. You have all given me a new lease on life.

Sincerely,
Eric S

Robert S

May 11, 2021

by Robert S on Donald Corenman, MD, DC

Back Fusion Surgery

I had my entire lumbar spine fused in November of 2018. I had scoliosis , with pinched nerves that were so painful I could hardly walk - and standing for more than a few minutes was impossible. Even sitting was painful.
The fusion surgery produced immediate relief! And the recovery was much easier than I expected.
To this day I can do all the activities I love from hiking, to standing in a stream fly fishing to riding my bike long distances - or just walking down the street with my wife.
Kudos to Dr. Corenman and his staff, (including the two Erics) for taking such good care of me!

Leslie R

Jul 9, 2020

by Leslie R on Donald Corenman, MD, DC

TLIF

I had my TLIF surgery on 6/24/2020 by Dr. Corenman, I can not say enough good things about the Dr or his staff. I was always treated with respect and explained everything throughly, that made it easy for everyone to understand. I highly recommend Dr. Corenman and the Steadman Clinic.

Home Testing For Leg Weakness