The Real Cause of Plantar Fasciitis
By James Speck via Somastruct.
fasciitis is a poorly understood condition. There is little consensus among
medical professionals about what causes the problem, and no treatments have
been reliably proven to treat it. A number of theories exist for why
plantar fasciitis develops, but the ineffectiveness of conventional treatments
suggests something is missing.
fascia is a band of connective tissue that runs along the underside of
the foot from the heel to the toes. The fascia helps maintain the integrity of
the arch, provides shock absorption, and plays an important role in the normal
mechanical function of the foot.
Plantar Fasciitis Is Not Inflammation
fasciitis was previously believed to be inflammation of the fascia near its
insertion on the heel bone. The suffix (-itis) means inflammation. Studies,
however, reveal that changes in the tissue associated with the injury are
degenerative and not related to inflammation, at least not in the way most
people typically think of inflammation.
onset of heel pain may indeed be related to acute inflammation. For persistent
heel pain, the condition more closely resembles long-standing degeneration
of the plantar fascia near its attachment than inflammation. This could explain
why anti-inflammatory medications and injections have been unsuccessful at
treating it. But there is more to heel pain than just the plantar fascia.
Not Just Fascia
pain associated with plantar fasciitis is localised to the underside of the
heel towards this inside of the foot. Often overlooked when talking about this
injury are the muscles that share an insertion with the plantar fascia. Looking
at the muscles in the sole of the foot you can see that the flexor
digitorum brevis muscle runs directly above the plantar fascia. On the
inside part of the heel the abductor hallucis, an important arch
stabilizer muscle, attaches.
not certain that the pain associated with this condition originates in the
plantar fascia. Many of the diagnostic features seen with this condition
(e.g. bone spurs, thickened fascia) are also found in people without heel pain,
and likewise may be absent in people presenting with the injury.
There’s a fair chance the pain is the result
of a tendon problem of the muscles deep to the fascia, rather
than the fascia itself. The role the foot muscles play in this condition will
be discussed later in the article.
most common theory on how plantar fasciitis develops is that repeated strain on
the fascia causes small tears to develop that eventually lead to pain.
Excessive pronation (collapse of the arch) is often cited as the cause of
increased mechanical loading of the fascia.
how frequently pronation is blamed, there is not much evidence that arch
mechanics play a role in the condition. This may be partly due to the difficulty researchers have accurately
measuring pronation, especially movement of the arch inside of a shoe. This
might also mean though that tensile stress on the fascia from arch movement, at
least in itself, is not a cause of plantar fasciitis.
Role of Compression
studies suggest repeated mechanical loading alone may not be enough to cause
degeneration of connective tissue. Tissue degeneration is more likely to occur
in areas that receive a poor blood supply, or at locations in the connective
tissue where the blood supply is cut off.
interesting finding is the presence of fibrocartilage near the attachment of
the plantar fascia. Fibrocartilage insertions are more common in structures
that undergo bending or compressive forces. It may be that bending
and compression are a bigger problem than tensile or stretching forces.
spurs were also once
thought to be a feature of this condition, with the thinking that they were
caused by the fascia pulling away from the bone. New evidence strongly suggests
that spurs are unlikely to be a cause of fasciitis, and that they
may develop due to compression rather than tensile force on the fascia.
no single factor has been reliably identified as contributing to the
development of plantar fasciitis.
two risk factors with the most support from current research:
- Decreased ankle dorsiflexion
- Increased Body Mass Index (BMI) in
factors are related in that:
- Both lead to increased strain on the arch
- Both lead to increased compression on the
dorsiflexion range of motion (ankle flexibility) is lacking, the body
compensates by increasing movement of the arch. In this way, decreased ankle dorsiflexion influences
pronation and places strain on
the underside of the foot.
having a high BMI causes strain because it places a load on the foot that may
be in excess of what the foot can support.
mentioned earlier, overpronation is thought to be a contributing factor, but
studies on this have so far produced mixed results.
second way these factors relate to each other is in the way people stand. A lack of ankle flexibility and a high BMI
can both cause increased pressure on the heel in standing. Keeping
weight on the heels causes compression under the heel. But it also means the
muscles and ligaments in the arch are not being used to balance your body
weight. Lack of use, I suspect, is a greater danger than overuse.
beyond these potential contributors to heel pain though, there is one major factor
that overshadows them all–the way footwear alters the normal function of the
A Major Factor: Shoes
are several features in the design of shoes that can directly cause abnormal
stress on the plantar fascia and potentially contribute to disuse of the
muscles in the foot.
written before about the link between a shoe’s toe spring and plantar fasciitis.
Most shoes curve up in the front in the area of the toes. This upward curve of
the sole is called a toe spring. This is engineered into footwear because shoes
are crudely made compared to the complexity of the structure and function of
curve allows for a rocking motion to occur as a person transfers their weight
from their heel to the front of their foot. This rocking motion is a substitute
for the bending the foot does when walking barefoot–a motion shoes are unable
this toe spring means that, for the majority of the time when a person is
standing or walking in a shoe, their toes are held elevated off the ground. The curvature of the sole places the
toes in an extended position. Because of this, the toes can only make contact
with the ground when the heel lifts up.
the toes splinted in this extended position can hypothetically do several
- Holds the plantar fascia and other structures
in the sole of the foot in an unnaturally elongated position
- Prevents the toes from gripping the ground
- Prevents the intrinsic foot muscles from
contracting to support the arch
- Prevents the muscles and plantar fascia from
assisting with shock absorption
- Possibly cuts off circulation on the
underside of the foot
walking barefoot the toes make contact with the ground much sooner in the
stance phase of gait than they do inside a shoe. These foot muscles are needed
to assist with gripping the ground and stabilizing the arch.
support from these intrinsic foot muscles, extra strain is placed on the
plantar fascia. This extra stress is can be doubly bad because the toe
spring also places the plantar fascia in a stretched position. Toe
extension (upward movement) stretches the plantar fascia via the windlass
mechanism. With the plantar fascia already stretched by the toe spring at the
time the foot contacts the ground, its ability to lengthen farther and absorb
forces is limited.
spring and a rigid sole are a bad combination. Increased strain on the fascia
is not the only problem related to the restricted movement of the toes though.
Deep to the plantar fascia are those foot intrinsic muscles with tendon
attachments to the heel.
is one theory on how connective tissue injuries happen. Stress-shielding
suggests that the part of a tendon exposed to a low amount of strain is
where problems develop. This contrasts sharply with the conventional theory
that excessive strain is the cause of heel pain.
possible that the restricted movement of the toes leads to degeneration of
either the plantar fascia or the tendons of the intrinsic muscles because while
wearing a shoe those structures are not put under enough tensile
stress! Tissues need movement to remain healthy!
only do shoes restrict the ability of the toes to contact the ground, they also
limit their ability to fully extend. When going barefoot extension of the
big toe is somewhere around 48 degrees. The toe only extends to about 28
degrees when wearing a standard shoe with an orthotic. Because of this, the
tissue on the underside of the foot is prevented from moving through a full
range of motion. Keeping the foot in such a fixed position for long periods of
time during the day could certainly lead problems.
Arch Supports Not Needed
arch not only supports the weight of the body, it also provides a space
underneath the foot for nerves and blood vessels to pass. A structural arch is
supported at its ends, not in the middle. Propping the arch of the foot up with
an arch support in a shoe doesn’t make sense. The built up arch in a shoe
can also alter circulation to the tissue attached to the heel, and it places
additional compression force on the underside of the foot.
to the toe spring, a shoe with a rigid sole also alters the natural movements
of the foot. Here is a comparison of how a “supportive” running shoe can bend
compared to a “barefoot” style shoe.
supportive shoe has very limited motion, which means it’s going to force the
foot to only move a certain way. It has almost no ability to twist, and it bends
only at one point along the forefoot. All individuals are built differently.
It’s very likely that the few spots where a stability shoe bends aren’t matched
perfectly with where your foot can bend and twist. Contrary to traditional
thinking, an overly rigid sole is probably worse for the plantar fascia than a
flexible one. A rigid sole forces the foot to move not based on anatomy, but in
the way the shoe manufacturer thinks a person’s foot should move.
traditional shoes typically are higher in the heel than in the forefoot by at least 10mm. This might not
directly affect the plantar fascia, but the raised heel does a couple of
- It places the ankle in a plantar flexed
(downward pointed) position which can lead to adaptive shortening of
the calf muscles. As noted early, calf inflexibility is suspected as major
risk factor for developing plantar fasciitis.
- It alters the way a person distributes their
weight on the foot.
- Lastly, the extra cushioning under the heel
causes you to strike the ground harder with your heel!
My History With Plantar Heel Pain
seven years I developed plantar fasciitis in my left foot. A few months earlier
I started wearing running shoes and inserts recommended to me by a specialty
running store. The “expert” from the store said the shoes and insoles would
help with my pronation. I wasn’t running much at the time. My BMI was in the
normal range. But I was wearing the shoes for work, standing and walking around
in them for eight or nine hours every day.
tried stretching, ice, taping–all the current recommendations for plantar
fasciitis–and none seemed to help. The pain lasted for several months.
treatment finally worked?
rid of the shoes. A short time after I stopped wearing those particular shoes
and insoles the pain went away. Coincidence? Maybe. At the very least that
experience convinced me that supportive shoes and orthotics are not a good
treatment for plantar fasciitis. If anything, they are the main cause!
Recap The Effects of Footwear
summarise, modern shoes do several things to the underside of the foot and
- Limit the natural movement of the foot
- Prevent muscle activity of the muscles that
insert on the heel
- Hold the plantar fascia in a stretched
- Reduce circulation on the underside of the
- Cause a heavy heel-striking gait
effects are more pronounced in stability or motion control shoes, but features
like the toe spring are present even in “barefoot” style footwear. Most
minimalist shoes on the market have substantial toe springs.
shoes enough to cause plantar fasciitis by themselves? Maybe.
combining a shoe that restricts motion and muscle activity in the foot with
increased stress, especially compressive stress, certainly could.
fasciitis, or better termed chronic plantar heel pain, is likely caused by a
- Heel Compression: from standing with weight
distributed on the heels
- Abnormal stress on the foot: from decreased
ankle flexibility, pronation, or a high BMI
- Footwear: particularly a rigid sole and toe
spring, which interferes with foot muscle activity, restricts circulation, and
hinders the plantar fascia’s ability to absorb forces
to popular belief, the condition is not caused by inflammation in the
traditional sense, and supportive footwear is possibly more
likely to contribute to the problem than help it.
fasciitis doesn’t develop from overuse or too much stress on plantar fascia. It
happens when the wrong kind of stress replaces the good kind of stress that the
foot needs to remain healthy. The aim of treatment, therefore, should not be
reducing stress on the arch. Instead, treatment should focus on changing the
types of stresses being applied and encouraging normal function of the foot.
is Part 1 in a three-part series on Plantar Fasciitis.
on to Part 2 to learn what studies say about the most commonly
used treatments, or skip ahead to Part
3 to learn how to treat
SC, Smeathers JE, Urry SR, Hennig EM, Hills AP. The pathomechanics of plantar
fasciitis. Sports Med. 2006;36(7):585-611.
TG, Martin RL, Cornwall MW, Wukich DK, Irrgang JJ, Godges JJ. Heel pain–plantar
fasciitis: clinical practice guidelines linked to the international
classification of function, disability, and health from the orthopaedic section
of the American Physical Therapy Association. J Orthop Sports Phys Ther. 2008
J. Plantar fasciitis. BMJ. 2012 Oct 10;345:e6603.
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