The three most common foot problems I see as a physical therapist are plantar fasciitis, bunions and Morton’s Neuroma. Today you will learn about all three and how they are all connected by one common cause.

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This is part 4 of a series titled “Foot Pain (How To Fix ‘Plantar Fasciitis’ and Other Common Foot Problems)”  

Part 1: Introduction 

Part 2: Foot Anatomy 101 (Normal Vs Natural)  

Part 3: How Shoes Change Your Foot 

Part 4: Foot Injury Anatomy 101

Part 5: How To Screen Your Foot Pain – Coming Soon…

Part 6: Foot Pain – The Rebuilding Process – Coming Soon…

Part 7: Foot Pain – Should You Wear Orthotics?  – Coming Soon…

Part 8: Foot Pain – What About Steroid Shots? – Coming Soon…

Injury Anatomy 101

The plantar fascia is a thick sheet of connective tissue that lies on the bottom of our feet. It runs from your inner heel bone (called your calcaneus) and fans out under your foot, attaching to the base of each toe. It is designed to provide support like a shock absorber for the main arch of the foot (called the medial longitudinal arch) when weight bearing. 

Think of the plantar fascia like a rubber band. When resting with your foot relaxed, the rubber band is loose and your foot is fairly mobile. As the foot hits the ground when walking or running, the plantar fascia is suddenly pulled taut (like a rubber band being pulled in both directions).1 This stiffening effect is crucial for two reasons. 

First, it helps the foot maintain its arch and control on the amount and timing of movement (from supination into pronation) during the stance phase of walking or running. Second, it transforms the foot into a more rigid platform allowing the body to push off the ground propelling itself forward. 

Imagine for a moment trying to trying to walk or run through quicksand. Without a rigid surface to push off from, it becomes extremely difficult to propel your body forward! The stiffening effect of the plantar fascia (called the “windlass mechanism”) essentially changes the quicksand into firm ground allowing your body to move effortlessly down it’s chosen path. 

Most people who are given a diagnosis of “plantar fasciitis” have pain on the bottom of their foot (usually near inside side of the heel) that is especially excruciating when taking their first few steps in the morning after waking up like Julie from our prior story. The most common description of this sensation from my patients is, “A knife stabbing the bottom of the foot with each step.” While these symptoms may lesson briefly during the day, they are often made worse with loading. This means the longer you stand, walk, run, the worse the pain becomes. 

Up until the early 2000’s, we labeled pain on the bottom of the heel as “plantar fasciitis.” The ending or suffix of that name “itis” implies inflammation of the plantar fascial ligament. The consensus amongst medical practitioners in the past was that “plantar fasciitis” was an overuse injury where the plantar fascia became irritated, inflamed and torn by repetitive stresses placed upon it.2

For years, the first step to treating this injury was to try and decrease inflammation with ice, medications and rest. When this didn’t work, orthotics were used to help support the arch of the foot (and limit excessive pronation) along with physical therapy (consisting of foot/calf stretching and strengthening exercises).3,4 If all else failed corticosteroids would be injected into the foot and eventual surgery may be recommended.5Unfortunately these methods don’t work for a lot of people (which is why close to 50% of those diagnosed with “plantar fasciitis” still have foot pain 15 years after it starts).6

Fortunately, our understanding of this troublesome injury changed in 2003 due to a groundbreaking article by Dr. Harvey Lemont.7 Dr. Lemont was not only a podiatrist but also a dermatopathologist (someone who specializes in looking at tissues of the body under a microscope to diagnose injury/disease). In one particular study, he took fifty of his patients with severe plantar fasciitis whose pain did not improve with traditional conservative treatments at the time (physical therapy, orthotics, medications, cortisone injections, etc.) and performed biopsies of the plantar fascial ligament. What he found shocked the medical world.

There were zero signs of inflammation in all fifty samples!

What he did find was dead or degrading tissue (called necrotic tissue). For years, the diagnosis of “plantar fasciitis” was given under the assumption it was driven by inflammation. Yet there was not any scientific evidence to support this claim! For this reason, Dr. Lemont recommended we stop incorrectly referring to this injury as “plantar fasciitis” and begin to refer to it as “plantar fasciosis” (as the “osis” ended refers to the degenerative process characterized by microtears and necrosis of plantar fascia).7

By now you may be asking, “How does a relatively healthy person get a piece of dead tissue in their foot?” 

The answer comes down to a problem with blood flow.

At first this can be confusing, as many who develop heel pain do not show any signs of circulation problems in their feet at first glance. The skin of the foot appears healthy. There is often hair on the tops of the toes and a strong pulse can be felt through the main arteries that bring blood into the foot (the posterior tibal artery and dorsalis pedis). However, as Dr. Ray McClanahan (a podiatrist who actually trained under Dr. Lamont) explained to me, it is when these patients put their relatively healthy foot into a shoe with a narrow toe box that the problem starts.8

When your big toe is pulled inward (the motion of adduction) within a narrow shoe, a muscle on the inside bottom of the foot called your abductor hallucis is put on stretch. You can actually see this stretching motion occur just under your big ankle bone (medial malleolus) if you passively move your big toe into this “modern shoe position.” This tightening of the abductor muscle leads to a pinching of a nearby artery that runs underneath called the lateral plantar artery (a small branch off the larger posterior tibial artery) which then restricts blood flow to a very specific part of the bottom of your foot in most people.9

In fact, a group of researchers in 2019 documented this phenomenon. In their study the investigators positioned their participants big toe into a narrow toe box position and then measured blood flow into the foot.9They found this smashed toe position created an immediate 60% drop in blood flow through the lateral plantar artery! While some people’s bodies were able to make up for this initial decrease in circulation and return to “normal” levels, two-thirds of the study participants continued to show a significant decrease in blood flow indicating little to no recovery in circulation. 

Poor blood flow limits the body’s ability to recover from stress. You see, every single day the tissues of your body (muscles, tendon and even bone) are in a constant process of fluctuation. When you place stress on your body (like when working out) portions of your tissues are degraded and then regenerated with the aid of sufficient blood flow. Overtime this natural replenishing process is how strength and capacity is built within the many tissues of the body. 

If we look specifically at the foot, the plantar fascia is placed under stress anytime you are weight bearing (walking, running, jumping, etc.). Those who remain barefoot as much as possible maintain healthy feet with very low incidence of injury such as plantar fasciosis.10,11

However, those who experience a loss of optimal blood flow to the bottom of the foot due to poorly fitting footwear are unable to optimally replenish and regenerate this tissue. Devoid of sufficient blood flow, the tissues on the inside of the heel that are supplied by the lateral plantar artery begins to degrade and symptoms of “plantar fasciosis” begin to set in.12-14 A large reason for this problem is the position of your big toe within narrow shoes! Consequently, this is the reason why bunions and plantar fascia pain are considered to be “cousins” (the greater the bunion deformity the increased risk of developing heel pain).15

Next, let’s talk about one of the most common forms of pain/injury to the forefoot. A Morton’s neuroma is a painful enlargement of a small nerve in your foot that runs between the third and fourth toes. This condition is most commonly seen in females over the age of 30. Just like with plantar fasciosis, we should always be asking ourselves, “Why is this nerve painful?” The answer is often inappropriate footwear.16-20

The three problem features of modern shoes (elevated heel, toe spring and a narrow toebox) all contribute to nerve irritation: 

Elevated heel: forces the toes into an extended position, which increases exposure to the nerve and therefore the amount of load on the nerve a you stand and walk.  

Toe spring: lifting the toes increases the load on the exposed nerve to an even greater degree and adds additional stretch.

Narrow toebox: pushes the bones of the foot together leading to a pinching of the small nerve that runs between the third and fourth toes.

This overload, stretching and pinching of the nerve is the perfect combination that can create symptoms of burning or electrical shock-like pain into the third and fourth toes.21 Along with these painful sensations, it is common to also have the feeling of “a pebble in the shoe” when walking. 

That’s it for today’s blog article! Next week we’ll learn how you can screen for the cause of your foot pain! 

Until next time,

Dr. Aaron Horschig, PT, DPT, CSCS, USAW

Dr. Kevin Sonthana, PT, DPT, CSCS

References

  1. Bolgla LA, Malone TR. Plantar fasciitis and the windlass mechanism: a biomechanical link to clinical practice. J Athl Train. 2004;39:77-82
  2. Warren BL. Plantar fasciitis in runners. Treatment and prevention. Sports Med. 1990 Nov;10(5):338-45.
  3. Kwong PK, Kay D, Voner RT, White MW. Plantar fasciitis. Mechanics and pathomechanics of treatment. Clin Sports Med. 1988 Jan;7(1):119-26. 
  4. Chandler TJ, Kibler WB. A biomechanical approach to the prevention, treatment and rehabilitation of plantar fasciitis. Sports Med. 1993 May;15(5):344-52. 
  5. Tallia AF, Cardone DA. Diagnostic and therapeutic injection of the ankle and foot. Am Fam Physician. 2003 Oct 1;68(7):1356-62. 
  6. Hansen L, Krogh P, Ellingsen T, Bolvig L, Fredberg U. Long-term prognosis of plantar fasciitis a 5-to 15-year follow-up study of 174 patients with ultrasound examination. Orthop J Sports Med. 2018;6(3):1–9. 
  7. Lemont H, Ammirati KM, Usen N. Plantar fasciitis: a degenerative process (fasciosis) without inflammation. J Am Podiatr Med Assoc. 2003 May-Jun;93(3):234-7. 
  8. McClanahan, R. Personal communication, July 29th 2021. 
  9. Jacobs JL, Ridge ST, Bruening DA, Brewerton KA, Gifford JR, Hoopes DM, Johnson AW. Passive hallux adduction decreases lateral plantar artery blood flow: a preliminary study of the potential influence of narrow toe box shoes. J Foot Ankle Res. 2019 Nov 4;12:50.
  10. Robbins SE, Hanna AM. Running-related injury prevention through barefoot adaptations. Med Sci Sports Exerc. 1987 Apr;19(2):148-56.
  11. D’Août K, Pataky TC, De Clercq D, Aerts P. The effects of habitual footwear use: foot shape and function in native barefoot walkers. Footwear Science. 2009;1(2):81-94
  12. Grasel RP, Schweitzer ME, Kovalovich AM, Karasick D, Wapner K, Hecht P, Wander D. MR imaging of plantar fasciitis: edema, tears, and occult marrow abnormalities correlated with outcome. AJR Am J Roentgenol. 1999 Sep;173(3):699-701.
  13. Tountas AA, Fornasier VL. Operative treatment of subcalcaneal pain. Clin Orthop Relat Res. 1996 Nov;(332):170-8. 
  14. Snider MP, Clancy WG, McBeath AA. Plantar fascia release for chronic plantar fasciitis in runners. Am J Sports Med. 1983 Jul-Aug;11(4):215-9.
  15. Cobden A, Camurcu Y, Sofu H, Ucpunar H, Duman S, Kocabiyik A. Evaluation of the Association Between Plantar Fasciitis and Hallux Valgus. J Am Podiatr Med Assoc. 2020 Mar 1;110(2):1-6
  16. Younger AS, Claridge RJ. The role of diagnostic block in the management of Morton’s neuroma. Can J Surg. 1998 Apr;41(2):127-30.
  17. Wu KK. Morton neuroma and metatarsalgia. Curr Opin Rheumatol. 2000 Mar;12(2):131-42. 
  18. Bennett GL, Graham CE, Mauldin DM. Morton’s interdigital neuroma: a comprehensive treatment protocol. Foot Ankle Int. 1995 Dec;16(12):760-3.
  19. Colò G, Rava A, Samaila EM, Palazzolo A, Talesa G, Schiraldi M, Magnan B, Ferracini R, Felli L. The effectiveness of shoe modifications and orthotics in the conservative treatment of Civinini-Morton syndrome: state of art. Acta Biomed. 2020 May 30;91(4-S):60-68.
  20. Bhatia M, Thomson L. Morton’s neuroma – Current concepts review. J Clin Orthop Trauma. 2020 May-Jun;11(3):406-409.
  21. Kay D, Bennett GL. Morton’s neuroma. Foot Ankle Clin. 2003 Mar;8(1):49-59.