2. The human foot has two equally important
functions :
(i) to support the body weight during
standing, walking, running or jumping;
(ii)to act as a lever to propel the body
forwards during propagation.
During all such activities the foot also acts as
a shock absorbing mechanism.
To fulfill the first need the foot has been built
as an adequate platform on which the
stresses of standing and moving are
spread evenly. The platform, to have best
efficiency, is pliable enough to adapt itself
to uneven or sloping surfaces.
3. To fulfill the second need, the foot has been
transformed into a strong and adjustable
lever which does not collapse under body
weight or powerful muscular thrust.
If the foot had been constructed of a single
strong bone instead of a series of small
bones, it could act as a platform to sustain
the body weight and serve well as a rigid
lever for progression.
But such an arrangement would fail to adapt
itself to uneven surfaces, and all forward
propulsive actions would entirely depend
on the activities of the gastrocnemius and
soleus.
4. Moreover, fracture in the foot would have been a
day to day incident due to absence of the
mechanism for absorption and dispersion of
shocks received in the plantar aspect of foot.
Because the lever is segmented with multiple
joints, the foot is pliable and can adapt itself to
uneven surfaces.
Moreover, the long flexor muscles of the digits
and the small intrinsic muscles of the foot can
exert their action on the bones of the forepart of
the foot and toes and greatly assist the forward
propulsive action of the triceps surae.
A segmented structure can hold up weight only if
it is built up in the form of an arch. Arching of
foot also enhances the action of the intrinsic
muscles of the foot and the long flexors of the
digits for progression.
5. FOOT AS A SUPPORTIVE MECHANISM
Human foot normally presents an arched form in its
skeletal basis. Pedal arches are present since
birth. In infants, the concavity in the sole due to
the pedal arches is not apparent because of the
great deposition of fat in their sole. But on x-ray it
is found that an infant has a more marked pedal
arch than an adult. On examination of an
articulated skeleton or a lateral x-ray of the the
foot or the imprint of a wet foot on the floor, it is
noted that the heel, lateral margin, the ball of foot
(part underneath the metatarsal heads) and the
pads of the distal phalanges touch the ground.
The medial margin of the foot arches up between
the heel and the ball of the great toe forming a
visible medial longitudinal arch.
6. The lateral margin of the foot is in contact
with the ground but its constituent bones do
not bear with equal pressure on the ground.
As on the medial side, there is also a bony
longitudinal arch on the lateral side
extending from the heel to the heads of the
metatarsal bones. This lateral longitudinal
arch is much flatter than the medial one.
There are also transverse arches that in
reality form half an arch. When both feet are
brought in contact with each other the dome
is completed. The arches vary in height in
different individuals, and being dynamic the
height may vary in the same individual in
different phases of activity.
7. FUNCTIONS OF THE ARCH
1.To support the body weight efficiently
and most economically.
2.To help in forward propulsion of the
body.
3.To protect the plantar vessels and
nerves from compression.
4.To act as shock absorbing mechanism
and minimize the stress of walking,
jumping, running etc.
8. MEDIAL LONGITUDINAL ARCH
• It has a marked height and is contributed by
calcaneus, talus, navicular, three
cuneiforms and medial three metatarsals
(from behind forward).
• The summit of the arch is at the superior
articular surface of the body of talus.
• Pillars through which weight is transmitted
to the ground are formed by the medial
tubercle of calcaneus posteriorly and heads
of the medial three metatarsals anteriorly.
• Due to the presence of several joints this
arch is weak; but because of so many
segments it is more resilient.
9. Factors for its maintainance
1. Bony configuration – Bones are faceted at different angles
so as to fit one another to form an arched configuration.
Bones are mostly wedge shaped with the narrower edge
being directed towards the plantar surface. The rounded
head of talus in the centre of the arch acts as the key
stone.
2. Intersegmental ties – These are formed by all the
interosseus ligaments (especially those binding the talus
and calcaneus together) and the dorsal and plantar
ligaments binding the tarsals and the bases of the
metatarsals with one another.
The most important ligament supporting the medial arch is
the plantar calcaneonavicular ligament, whose upper
surface supports the head of talus. This ligament is itself
supported from below by a slip of tibialis posterior tendon.
If this ligament is stretched the navicular and calcaneus
move away from each other and the head of talus sinks
lower between them.
10. 3. Tie-beam arrangements – The medial part of
the plantar aponeurosis, flexor hallucis
brevis, abductor hallucis, and the tendons of
the flexor digitorum longus and flexor
hallucis longus tie the two ends of the pillars
and prevent separation of the ends of the
pillars of the arch like bow string or tie beam.
During standing with body weight only to support,
there is a tendency to relax the intrinsic and
extrinsic muscles of the foot and to rely upon the
tension of the plantar ligaments, particularly the
plantar aponeurosis, to tie the bones into their
arched form.
11. The muscles do this job only if the
longitudinal arches are allowed to sink. The
less the feet are close together, the less the
medial arch is elevated. Overwhelmingly
efficient as a tie beam is the tendon of flexor
hallucis longus.
• This bulky muscle mass beneath the soleus,
even spares a slip to assist the pull of its
weaker sister – the flexor digitorum longus.
It is highly significant that this slip acts only
on the tendons of 2nd and 3rd toes – the
remaining members of the medial
longitudinal arch.
12. • However, this important factor is not called into
play during short periods of standing with only
body weight to support. But during prolonged
standing relief from stretching of the ligamentous
ties is offered by contraction of the long digital
flexors which not only maintain the arch but also
takes off some load from the metatarsal heads by
pressing the pads of the toes to the ground.
• During movements of propulsion or landing on the
feet, the momentum of the body throws a greater
strain on the arch. Much of this strain is taken up
by the contraction of flexor hallucis longus.
• Unlike the ligaments the short muscles have the
advantage of having the capacity to adjust the
length of the tie-beam. The plantar aponeurosis is
capable of being tightened by dorsiflexion of the
toes.
13. 4. Sling arrangement – The tendons of tibialis
anterior and tibialis posterior suspend the
arch from above like a sling and help to
maintain the arch.
They act by their tendency to invert and
adduct the foot i.e., by raising the medial
border from the ground.
As they do not have any direct pull tending
to approximate the pillars of the arch, they
are less important in maintaining its
integrity.
14. LATERAL LONGITUDINAL ARCH
• This arch has very little height and is
contributed by calcaneus, cuboid and the
lateral two metatarsals (from behind
forwards).
• The summit of the arch is at the subtalar
joint.
• The ends of the pillars, for weight
transmission, are formed by the medial
tubercle of calcaneus (here both the
longitudinal arches meet) and by the heads
of the 4th and 5th metatarsals.
15. LATERAL LONGITUDINAL ARCH
• Because of fewer bones and joints, this
arch is less resilient than the medial arch.
• It is built to transmit weight and thrust to the
ground rather then to provide a mechanism
for absorption of such forces.
• It makes more extensive contact with the
ground under the stress of weight and
thrust.
• As the arch flattens, an increasing fraction
of the load is transmitted through the soft
tissues inferior to the whole of the arch.
This can easily be appreciated by noting
the foot print of a normal person.
16. Factors for its maintainance
1.Bony configuration – As in the medial
longitudinal arch, the shape of the bones
helps to form and maintain the arch. A
triangular backward bony projection from
the inferior border of the proximal articular
surface of cuboid is an important bony
configuration to maintain the upward tilt of
the long axis of the calcaneus.
2.Intersegmental ties – The long and short
plantar ligaments are the most significant of
the intersegmental ties for the lateral arch.
They play more important role than in the
case of medial arch.
17. Factors for its maintainance
3. Tie-beam arrangements – The lateral part of
the plantar aponeurosis, flexor digiti minimi
brevis, abductor digiti minimi, and the tendons
of the flexor digitorum longus and brevis to the
4th and 5th toes all assist strongly by
preventing separation of the ends of the
pillares like bow string or tie beam.
4. Sling arrangement – The peroneus brevis and
peroneus tertius tendons act as slings to tie
the lateral border of foot from above. The
tendon of peroneus longus by winding around
the lateral border of foot and passing below
the cuboid is the most significant single factor
in maintaining the integreity of the lateral arch
by sustentacular mechanism.
18. TRANSVERSE ARCH
• Since the sole is transversely concave,
conventionally existence of a series of transverse
arches are described even though transverse arch
is a half arch.
• When the medial borders of both feet are brought
together, a complete transvers arch is formed
because the lateral longitudinal arches lie lower
then the medial arches.
• The metatarsal heads make contact with the
ground and do not participate in formation of
transverse arch.
• The transverse arches mainly involve the bases of
the metatarsals, the cuneiform and the cuboid.
Transverse arch is best seen in the region of the
tarsometatarsal joints.
19. Factors for maintenance
1. Bony configuration – The cuneiform bones, the bases of
the metatarsals and the cuboid are all wedge shaped,
being narrower on their plantar surfaces. This
arrangement gives the plantar surfaces of the bones a
much smaller radius of curvature than their dorsal
surfaces and forms a transverse arch.
2. Intersegmental ties – The interosseus ligaments, deep
transverse ligaments, plantar ligaments and the oblique
and transverse heads of adductor hallucies tie the
component bones of the arch together to help in the
maintainance of the transverse arch.
3. Tie-beam arrangement – Tendon of peroneus longus as
it passes from the lateral border to the medial border of
the foot is a strong agent in maintaining the transverse
arch. The tibialis posterior also helps in the same way.
They approximate the medial and lateral borders of the
foot across the sole.
20. • Role of muscles and ligaments in
maintaining the pedal arches –
Pedal arch is a dynamic arrangement
and the skeletal, ligamentous and
muscular factors in the formation and
maintenance of the arches are
inseparable from each other. In cases
of muscular insufficiency, the plantar
ligaments get stretched, bony
configuration gradually changes and
ultimately flat foot develops due to loss
of the arches. Hence muscles are
indispensible for the maintenances of
the arches.
21. • Ligaments are definitely important but
alone they are inadequate to maintain
the arches. It has been shown that
during standing erect on the foot
(without any other load to support) the
ligaments are sufficient to maintain the
pedal arches. The intrinsic and
extrinsic muscles of the foot are
relaxed at this stage. But as soon as
one changes from a static to a dynamic
posture the muscles become active to
maintain and even to accentuate the
arches as is seen just before toe-off
phase during walking.
22. Abnormalities of the arches of foot
1. Flat foot – As the arch of foot becomes inefficient,
the head of talus is no more supported. It drops
and forces its way between the medial malleolus
and the tubercle of the navicular bone. Thus the
fore-foot is deflected laterally and the normal
concavity of the medial border of foot is replaced
by a convexity. There is loss of the plantar
concavity as the arches get flattened. The plantar
vessels and nerves are compressed and this
produces pain in the metatarsal region of the foot
(metatarsalgia). The pain radiates towards the
toes. Rapid gain in body weight, loss of tone of leg
muscles, prolonged standing may be causes of
acquired flat foot. Flat foot is often congentital.
2.Talipes equinus – The heel is raised, the foot
points downwards (like ungulates) and is fixed in
plantar flexion. The patient walks on toes.
23. Abnormalities of the arches of foot
3. Talipes calcaneus – Heel is weight bearing and
toes are upturned due to fixed dorsiflexed
position of ankle. Patient walks on heels.
4.Talipes varus – The foot is fixed in inverted
position. Patient walks on lateral border of foot.
5.Talipes valgus – The foot is fixed in everted
position. Patient walks on medial border of
foot.
6.Talipes equinovarus (club foot) – Foot is fixed
in inverted position and the heel is raised.
7.Talipes equinovalgus – Foot is in everted
position and the heel is raised.
24. FOOT AS A PROPULSIVE MECHANISM
• During normal walking each lower limb passes
through a series of successive swing and stance
phases.
In Swing phase the lower limb is off the ground and
accounts for only 1/3rd
of the walking cycle period.
In stance phase, the limb strikes the ground and
bears weight. It accounts for 2/3rd
of the cycle.
A walking cycle includes the period from the heel
strike of one foot to the next heel strike of the
same foot. The cycle of one limb alternates with
the other. Hence during walking there is never a
period when neither of the lower limbs are on the
ground. Thus single support phase alternates with
double support phase.
The stance phase has 3 stages : Heel strike, midstance,
and toe-off.
Swing phase has 2 stages : Early swing and late swing.
25. Heel strike – As the heel strikes the
ground for stepping forwards, the
muscles acting on the hip (especially its
abductors and the adductors) stabilize
the pelvis on the femur of the weight
bearing limb. The knee extensors
stabilize the slightly flexed knee (150-
170 degree). The hamstrings and the
gluteus maximus extend the hip to
propel the trunk forwards.
26. Midstance – The dorsiflexors of the ankle now elongates
by controlled relaxation and the plantar flexors
contract. The forefoot moves gently downwards to
come in contact with the ground. Gradually the lateral
border of the foot starting from the heel rolls into
contact with the ground until all the metatarsal heads
are grounded. The arches of the foot are much
lowered and the foot becomes much flatter.
Simultaneously the foot is supinated to bring about
maximal contact with the ground. The ankle
dorsiflexors now become active and pull the tibia
forwards moving the centre of gravity anteriorly.
27. Toe off – The triceps surae begin to lift the heel off
the ground and the quadriceps extend the slightly
flexed knee. As it is maximally lifted, the body is
moved further forward and the weight is
transferred to the metatarsals and phalanges. The
peroneus longus and brevis now pronates the foot
and there is accentuation of the medial
longitudianl arch. The whole weight is now
transferred to the ball of the great toe which is the
last part of the foot to leave the ground. The flexor
hallucis longus gives a final strong planter flexion
which pushes the body off from the great toe. The
momentum raises the limb free from the ground.
28. • While the heel is rising from the ground, the toes are
gradually extended so that the plantar aponeurosis is
pulled and tightens the longitudinal arches.
• Contraction of the toe-flexors increases the take-off force
of the foot by the pressure of the toes on the ground.
Extension of the toes after the heel off stage also causes
elongation of the flexor tendons of the digits. This
increases the force of their subsequent contraction.
Contraction of the long flexors also helps by increasing the
force of plantar flexion at the ankle.
• The most powerful muscle acting in this way is the flexor
hallucis longus which acts on the big toe as well as on the
2nd and 3rd toes by the slip it gives to flex. digit. longus.
• The short flexors in the sole strongly assist the long
flexors in heightening the arch and in flexing the toes.
• The propulsive force so generated adds greatly to that of
soleus and gastrocnemius. Hence it is stated that the
tendocalcaneus has a ‘bottom gear’ (soleus part) and a
‘top gear’ (gastrocnemius part) mechanism and the flexors
of the toes provide an ‘over drive’.
29. Early swing phase – After the limb is free from
the ground the hip flexors swing the limb
forward and the knee becomes passively
flexed. The ankle dorsiflexors keep the foot
clear off the ground.
Late Swing Phase – The dorsiflexors of the
ankle make the foot ready for the heel
strike. The hamstrings now decelerate the
limb just prior to heel strike. There is
accentuation of the arches of the foot.
31. • During running the stance phase accounts
for only 1/3rd of the stride (40% during
jogging to 27% during sprinting). Hence
there is always an aerial phase when neither
of the lower limbs are on the ground. Most
runners strike the ground first with the heel.
But the centre of pressure moves very
rapidly distally to the heads of the
metatarsals where it remains for most of the
stance phase. The take off point is still the
anterior pillars of the medial longitudinal
arch due to pronation of the foot.
32. FOOT AS A SHOCK-ABSORBING MECHANISM
Foot is a reasonably good spring. When landing
at speed from a height, the toes and then the
forefoot takes the first thrust of the weight
before the heel strikes the ground (i.e. reverse
of taking off at maximum speed). Muscles play
an essential role in absorbing the shock of
landing. Besides the muscles the plantar
aponeurosis, long and short plantar ligaments
and the plantar calcaneo-navicular ligament are
all involved in the spring action and act as
shock absorber. The subcalcaneal fat pad also
act as cushions to absorb some amount of the
impact of landing.
