Peroneal Nerve Entrapment | Fibular Head of Knee

An Overview of Peroneal Nerve Entrapment

Peroneal nerve entrapment involves trapping of a peripheral nerve in a tunnel. These peripheral nerves are different from the nerves in the spinal canal (the radicular nerves) due to their “protective armor”, the epineurium and perineurium. This protective sheath makes the nerve less vulnerable to injury than the spinal nerves. Nonetheless, these nerves can be injured by stretch, impact and compression.

All of these nerve entrapment syndromes are very similar in their pathology (the basic disorder that causes the problem). This pathology is compression of the nerve by a bone or tendon. The difference in each disorder is the nerve distribution (where the nerve travels and what it does) and whether this nerve contains only sensory nerves, only motor nerves or a combination of the two.

You can read about the specifics of what causes the microscopic damage to a nerve in the separate topic “Nerve Injuries and Recovery” on this website.

If the compressed nerve has strictly a pure sensory distribution, no motor weakness will be present and therefore no atrophy can occur. Atrophy only occurs when the muscle belly shrinks due to a lack of nerve supply.

However, pain inhibition can cause temporary muscle weakness in certain leg positions. This is not true muscle weakness but an actual subconscious reflex to prevent pain from occurring by subconsciously refusing to contract the muscle for fear of pain.

We will first discuss the general symptoms that can occur with peripheral nerve compression.

Sensory Symptoms

With peroneal neuropathy, the nerve becomes compressed. As pressure increases on the nerve, the blood flow decreases. This causes nerve malfunction such as conduction loss and unintended conduction called ectopic stimuli. Loss of conduction means the nerve will not convey messages to the brain from the skin. This loss of sensation is obviously described as “numbness”.

Injury can also cause conduction to occur even when the nerve is not stimulated. This is like a short circuit in doorbell wiring making the doorbell ring when no one is at the door. The patient notes these sensations as pain, paresthesias (pins and needles) as well as bizarre sensations (ants crawling or cold water splashing on the skin).

The continued crush injury can also injure the myelin sheath, the “insulation” of the nerve. This can be more of a permanent injury. Myelin sheath injuries can heal but this healing takes between 8-14 weeks for recovery.

With compression of the nerve, increased “pins and needles” (paresthesias) typically occur. Electric shock sensations (Tinel’s sign) that “zing” down the nerve then can occur. Abnormal spontaneous hot and cold sensations can develop in the distribution of the nerve

With chronic injury, fluid collects in the space that the nerve occupies and the nerve itself can swell, increasing the intensity of the symptoms. Continued nerve injury can induce pain. Burning sensation can occur when the nerve develops permanent injury. The pain can worsen and spread. Pain tends to be worse with activity and is relieved by rest but continuous pain can occur with chronic injury.

Motor Symptoms

Motor strength loss typically occurs gradually. There are rare circumstances however where the entire muscle group can fail all at once. In the leg with peroneal neuropathy, this might manifest as foot drop, the inability to hold the foot up when walking. With foot drop, the foot will slap on the ground or even “catch”: the ground when the foot swings through when walking.

As small muscles lose their nerve supply they can create a “cramping feeling”. Cramping can be an indication of weakness but other non-related disorders can also cause cramping.

Causes of Nerve Entrapment Syndromes

Most nerve entrapment syndromes are caused by mechanical and genetic problems. Genetics have to do with the size of the tunnel these nerves travel in. Some people have congenitally smaller tunnels and with aging, previous injury, degeneration (bone spurs) and inflammation, these tunnels become crowded. Mechanically, overuse syndrome can cause tendons to swell (tendonitis and synovitis) and crowd out the nerve.

There are genetic and metabolic disease processes that can contribute to nerve malfunction. These processes may increase the swelling (crowding) of the tunnel or make the nerve itself more sensitive. These disorders include rheumatoid arthritis, hypothyroidism, pregnancy, diabetes, acromegaly (too much human growth hormone) and CMT syndrome (Charcot Marie Tooth syndrome-a genetic condition).

(Click to Enlarge Image) Peroneal Nerve Entrapment Pain Diagram.

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(Please keep reading below for more information on this condition.)

What is Peroneal Nerve Entrapment Syndrome?

The sciatic nerve splits into two nerves as it descends into the leg. Just above the knee, these split nerves are called the common peroneal nerve and tibial nerve. The common peroneal nerve then splits into the deep and superficial peroneal nerves right at the fibular head, the bone on the bottom outside of the knee joint.

To go back to anatomy, the lower leg has two bones, the tibia and fibula. The tibia is the main bone of the lower leg and makes up the bottom surface of the knee joint. The fibula is the smaller bone on the outside of the leg and acts as a strut rod, a stabilizer bone for the leg. It is this bone that the peroneal nerve wraps around.

The peroneal nerve is very superficial here (right under the skin) and exposed to potential injury. Injury can occur from impact (falling off a bicycle) or by being struck by a blunt object (a ski or hockey stick). Other actions that can injure the nerve are surgery (knee joint replacement or fracture) and even the chronic act of crossing the legs while sitting. Continuous wearing of high boots with tops that rest against the outside of the leg in this region or the use of ski boots can even set this injury off.

Symptoms of Peroneal Nerve Entrapment

This nerve supplies both motor and sensory fibers to the leg. The sensory portion of the nerve supplies the outside of the shin and the top of the foot (but not the first two toes). This region of the leg and foot will develop numbness and paresthesias (pins and needles). This is noted especially if the outside of the knee where the nerve was located (the fibular head) was struck by an object or continuous pressure was applied (crossing the legs). If symptoms are severe, the numbness can wake the patient up from a dead sleep.

The motor portion of the nerve supplies the muscles of the anterior and lateral aspect of the shin. These muscles are responsible for lifting the foot up when walking and preventing the foot from turning in when weighting the leg.

Motor nerve injury would then cause two particular symptoms of weakness, foot drop and inversion sprain. Foot drop occurs when walking. The foot will slap on the ground when the heel strikes the surface. Occasionally, the toes of the foot will “catch” the ground when the leg pushes forward and the patient can “trip over their own foot”.

The other noticeable weakness will be the “feeling” of the ankle wanting to “turn in” similar to the feeling of being on the verge of “spraining the ankle”. This is due to weakness of the ankle evertors, the peroneal muscles which prevent the foot from “turning in”.

Diagnosis of Peroneal Nerve Entrapment

History, examination and special testing confirm the diagnosis of this condition. The history is exactly like that noted above.

L5 nerve compression in the spinal canal from a herniated disc can look very similar to peroneal neuropathy so great care has to be used to differentiate peroneal nerve compression (rare) from L5 radiculopathy (common).

Testing essentially consists of one or two tests. The Tinel’s test has to do with the exquisite sensitivity of any nerve at an injury point. A nerve that is injured will fire an ectopic focus (a lightening bolt of electricity) down to the end of nerve when stimulated. Percussion of the injury area will elicit this “lightening bolt”. In the case of peroneal fibular head entrapment syndrome, the injury point is where the nerve wraps around the fibula. A positive test will cause an electrical “zap” into the foot with percussion of the peroneal nerve at this location.

Some physicians will perform a two-point discrimination test. This test uses the ends of monofilament fishing line on a tool that can separate these two points at a specific distance. This tool is used to determine the smallest distance that a patient can identify the distance between these two points. In peroneal nerve/fibular head entrapment syndrome, this distance will be larger than normal in the outside of the shin as the sensitivity of the skin here diminishes.

Finally, an electrical test called an EMG/NCV can be used to determine if there is conduction loss or muscle weakness. A negative test (no findings) would not preclude a diagnosis of peroneal nerve/fibular head entrapment syndrome.

Treatment of Peroneal Nerve Entrapment

Treatment depends upon the severity of the symptoms. Intermittent symptoms that do not bother the patient and do not wake them up at night generally do not need to be treated.

With increasing symptoms, medications such as NSAIDs (Motrin, Aleve) can be helpful. Steroid injections can rarely give relief.

If symptoms continue without relief or motor weakness occurs, surgical decompression of the nerve can provide long-term relief.

To learn more about peroneal nerve entrapment syndrome, or to discuss the fibular head of the knee in more detail, please contact the office of Dr. Donald Corenman, spine specialist and back doctor offering diagnostic and surgical second opinions to patients in the USA and around the world.

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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

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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.

Peroneal Nerve Entrapment at Fibular Head (Knee)