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Baxter’s Neuritis and Plantar Fasciitis

A rare nerve entrapement that can explain some stubborn cases of “plantar fasciitis”

Paul Ingraham, updated

Baxter’s neuritis is one of several possible causes of plantar fasciitis… sort of. You could consider it a separate condition that mimics plantar fasciitis… or you could say that it’s just one of several possible causes of heel pain that can be tricky to tell apart.

Plantar fasciitis is a common an overuse injury of the foot, notoriously stubborn, which plagues runners and people who have to stand on hard surfaces at work. It’s usually described as a kind of tendinitis of the arch, but that’s only one of several possible factors: like Baxter’s neuritis, heel spurs, calcaneal fatigue, and arch muscle trigger points. The name “plantar fasciitis” implies too much, and the condition should probably just be called plantar heel pain.1

Baxter’s neuritis, AKA distal tarsal tunnel syndrome, is entrapment of the first branch of the lateral plantar nerve. It’s rare, which is probably the best reason to regard it as its own condition, rather than a cause of plantar fasciitis. But when it occurs, it is often mistaken for plantar fasciitis.2 Podiatrist Dr. Patrick DeHeer:

Through my 23 years of practice, I often think of the old adage, “When you hear hoof beats, think horses, not zebras.” I consider myself a very good diagnostician. I base my diagnoses on comprehensive history and physical examination. However, there are times when the patient is not progressing as expected and those “hoof beats” are actually zebras. One such case is heel pain from Baxter’s neuritis, which is entrapment of the first branch of the lateral plantar nerve.

So although rare overall, it’s probably common enough among people with stubborn heel pain to be well worth considering.

Gray’s Anatomy, Plate 833, nerves of the bottom of the foot

Gray’s Anatomy, Plate 833, nerves of the bottom of the foot

Nerve entrapment primer

It seems obvious that pinching nerves will hurt, but in fact nerve trunks are surprisingly tolerant of physical stress. They have to be. As a general rule, concerns about “nerve pain” are overblown in our society, partly driven by advertisements for drugs to treat neuropathy.3

It takes more severe and persistent mechanical stress to piss off a nerve than most people realize. There are probably also subtle biological vulnerabilities that make us more prone to actually feeling a nerve pinch. For instance, a vitamin B12 deficiency might make an otherwise harmless entrapment into a real problem. There’s an excellent possibility that lots of people have lots of minor nerve entrapments all the time, but they are asymptomatic.

However, sometimes nerves get pinched harder, for longer, and/or the biological vulnerability is higher for some reason, and the result is peripheral neuropathy, which mostly causes pain, tingling, numbness, and weakness in the tissues supplied by the nerve. Some nerves are infamously more likely to get pinched than others, just because of their anatomical situation.

“Who thought it was a good idea to put this nerve here?!”

Baxter’s neuritis is probably a phenomenon because of the relatively vulnerable physical predicament of this nerve. As with everything else about plantar fasciitis, the main rehab challenge is that it’s so hard to reduce physical stresses in the foot without anti-gravity technology.

The lateral plantar nerve passes through the “tarsal tunnel,” which is similar the more famous carpal tunnel of the wrist, and Baxter’s neuritis could indeed be considered “the carpal tunnel syndrome” of the foot. The nerve then takes a sharp turn at the inside of the heel bone and travels diagonally across the arch towards the littlest piggy. It is the largest nerve that is more or less right in the arch of the foot. It’s the arch nerve.

When troubled, Baxter’s neuritis causes pain much like plantar fasciitis, but with some distinctive differences (which are all typical of neuropathy rather than tendinopathy):

Does any of that sound like you? If so, confirming or rejecting this diagnosis is a high priority: go see a neurologist.

Tarsal tunnel syndrome — a close cousin

Tarsal tunnel syndrome is closely related to Baxter’s neuritis, but involves the impingement of nerves just a little higher up, on the inside of the ankle, where they pass through the tarsal tunnel. Nerve entrapment at this location is more truly “the carpal tunnel syndrome of the foot” than Baxter’s.

Just like most cases of Baxter’s, TTS will be more obviously “nervy” than plantar fasciitis. But while Baxter’s affects just the arch, and thus is more easily mistaken for plantar fasciitis, TTS usually causes diffuse symptoms all over the bottom of the foot, making it much less likely to be mistaken for plantar fasciitis.

Also, there’s a very easy test for tarsal tunnel syndrome: firmly tap behind the inside ankle bone. If your symptoms will flare right up, bingo! This is called the “tarsal tap” test, a quick and easy way to confirm or deny tarsal tunnel syndrome.

An entrapped nerve does not necessarily mean you need surgery

When an entrapped nerve is confirmed as the cause of chronic pain problem, we all tend to assume that it needs to be cut free, like freeing a dolphin from a fishing net. And that certainly can work.

But it doesn’t always work, and it may not be necessary. The conservative approach treating nerve entrapments, in broad strokes, goes like this:

  1. Give it a rest, of course. Tissues rarely calm down and heal without being given a bit of an opportunity. This can be a tall order with foot problems, but that’s life — it’s the body parts we need the most that get hurt the most. Read more about the art of resting for rehab.
  2. Reduce your vulnerability and sensitivity to nerve entrapment generally. That is, try to identify and eliminate all factors that could be contributing not to the trap itself, but how much the entrapment hurts. This boils down to a broad-spectrum effort to improve your health and fitness in every possible way, starting with the lowest-hanging fruit. “A rising tide lifts all boats.”

END OF EXCERPT

This article is an excerpt of my popular plantar fasciitis tutorial, a 57,000-word e-book, regularly updated for over a decade, that reviews the nature of the beast in extreme detail, and every treatment option. Sales of e-books are how PainScience.com has been producing accessible, science-based advice for painful problems since the early mid-2000s. You can buy the whole book here, or read the free introduction first.

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Keep reading for free! The book page has a substantial free introduction, and there other free samples from the book and closely related articles:

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About Paul Ingraham

Headshot of Paul Ingraham, short hair, neat beard, suit jacket.

I am a science writer, former massage therapist, and I was the assistant editor at ScienceBasedMedicine.org for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.

What’s new in this article?

2019Publication.

Notes

  1. Riel H, Cotchett M, Delahunt E, et al. Is 'plantar heel pain' a more appropriate term than 'plantar fasciitis'? Time to move on. Br J Sports Med. 2017 Nov;51(22):1576–1577. PubMed #28219944. 

    “We propose the term ‘plantar heel pain’ to describe the condition of pain under the heel when no differential diagnoses are indicated and until further research is undertaken to arrive at a clear understanding of the appropriate terminology and associated diagnostic criteria.”

    The authors quite correctly point out that there are several possible causes of the condition that have nothing to do with the plantar fascia, and none of them correlate cleanly with symptoms. So an imprecise label is really the only honest one.

    See also: one-minute video summary of this paper.

    BACK TO TEXT
  2. Ferkel E, Davis WH, Ellington JK. Entrapment Neuropathies of the Foot and Ankle. Clin Sports Med. 2015 Oct;34(4):791–801. PubMed #26409596.  “Distal tarsal tunnel syndrome results from entrapment of the first branch of the lateral plantar nerve and is often misdiagnosed initially as plantar fasciitis.” BACK TO TEXT
  3. PS Ingraham. Nerve Pain Is Overdiagnosed: A story about nerve pain that wasn’t really nerve pain. PainScience.com. 1037 words. BACK TO TEXT

There are 178 more footnotes in the full version of the book. I really like footnotes (and I try to have fun with them).


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