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Dynamics of the Foot and Treatment of Foot Related Disorders
The foot is a functional unit made up of
bone, muscle, tendons, nerves and membrane.
The structure of the foot has changed very
little since prehistoric times. In fact, the
development of man’s brain occurred after
the development of the foot. Anthropologists
believe it was man’s ability to become
bipedal (walk on two feet) that allowed the
cerebral cortex to develop.
The foot is a complex structure.
Nearly ¼ of all the bones in the body are
in the feet (52 of them). Additionally,
there is a high concentration of nerve
endings in the feet, like the hands. The
unique structure of the foot allows it to
support the full weight of the human body.
It absorbs the shock of foot strike in
running and is rigid enough to “toe off” at
the end of the gait cycle. It does not
function alone, but works in conjunction
with the ankle, knee, hip and lower back.
The three phases of gait (walking).
- Heel strike: also known as proprioception or “finding the ground”.
The foot is in a position of Supination
(locked and rigid condition).
- Mid Stance: from heel strike to toe
off. This is the shock absorbing phase
where the foot becomes unlocked and the
knee travels over the foot. The foot
goes into a position of Pronation
(unlocked and flexible).
- Toe-off: weight transferred to the
ball of the foot. This allows the body
to propel itself over the toes. The foot
re-Supinates (locks up and becomes
rigid) to provide a lever for forward
momentum.
Where the problems with foot function
arise.
For the foot to function properly it must
be able to be locked (supinated) and
unlocked (pronated) at the required phases
of gait. Most foot function problems arise
during Mid- Stance. If the foot over
pronates it can cause stress on the plantar
fascia (plantar fasciitis or heel spurs),
shin splints and associated knee pain as a
result of excessive tibial torsions. For
those who feet are excessively rigid and do
not pronate enough (supinators) the problems
are typically inversion sprains, stress
fractures of the small bones in the feet,
knee problems associated with unnatural gait
and shock to the lower kinetic chain (ankle,
knee, hip, lower back). Many foot related
problems occur from “over use syndrome”.
“Over use” implies an injury that develops
gradually as a result of a change in
intensity of activity. For a runner this may
be increasing mileage or speed. For many, it
may be starting a new exercise program or
perhaps sudden weight gain like a pregnancy.
Often, an asymmetric (one side or the
other) foot, knee or back problem may be a
result of a leg length discrepancy. This is
very common among the population and is
rarely identified during routine
examinations. Leg length discrepancies of
3/8” to 5/8” are easily treated with a heel
lift (correcting to ½ the discrepancy). More
extreme cases may require shoe modification.
Problems resulting from leg length
discrepancy often do not manifest themselves
until the later years when the body is less
resilient.
How proper foot wear can address foot
problems.
Once you know what
type of foot you have, you should select
shoes that compliment your feet. If you have
a tendency to over pronate, look for a shoe
designed for control. Typically it will have
a straight last, substantial heel counter
and firm mid sole (not a cushioned model). A
shoe for normal feet will have a semi-curved
last and moderate cushion. Supinators should
choose shoes with a curved last and maximum
cushioning.
Have your feet measured with a Brannock
Device for overall length, arch length and
width. Try on both shoes in several styles.
Do the toe jam test. If your toes hit the
front of the shoe it may be too short or too
wide. If you wear orthotics, try the shoes
with them in.
Select a shoe that is appropriate for
your activity.
Running shoes are great for running and
walking (in line), court shoe for lateral
movements and aerobic shoes for indoor
exercise. Replace your shoes often. Worn
shoes contribute to foot problems. Running
shoes are good for about 1,000 miles. Do not
try to get extra miles, instead get new ones
and use the old for around the house if you
must. Many runners rotate a couple pairs to
get longevity.
What are Custom Foot Beds and
Orthotics and how do they work.
Custom footbeds and orthotics are inserts
that go into the shoe to provide correction
or accommodation for foot abnormalities.
Footbeds/orthotics also enhance foot
function and comfort in footwear. Designs
may vary depending on the footwear to be
worn and the type of correction required.
Most modern designs are made from semi-rigid
materials that work with the shoe to help
the foot function as normally as possible.
The foot can either be casted or an
impression taken which serves as model for
orthotic fabrication. Sport footbeds and
orthotics are transferable into most shoes
with a removable sock liner (insole). Dress
shoes rarely have the volume for a full
length design thus requiring a ¾ length
device. Good footbeds and orthotics treat
the problem, not just the symptoms.
How to Determine
Your Foot Type
A simple method for determining if your
foot is flexible or rigid is to take a
comfortable stance on a bare floor (not
carpet) with your feet apart at shoulder
width. First, look at each foot to evaluate
the natural arch height. Next, rotate you
hips to the left until you cannot keep the
ball of your left foot on the ground.
Evaluate the arch height for the left and
right foot compared to their natural arch
height.
Rigid feet will not show a significant
change in arch height. The flexible foot
will have a significantly increased arch
height on the left and a diminished arch on
the right. Reverse the hip rotation. Again,
the rigid foot will not exhibit a dramatic
change in arch height while the flexible
foot will now have increased arch height in
the right foot and diminished arch on the
left.
While the “normal” foot will exhibit
flexibility in this test, some arch profile
will be maintained when the foot is fully
pronated, as the right foot is when the hips
are turned to the left or the left foot is
when the hips are turned to the right. |
