A marvel of bioengineering, the human foot combines the
mechanical complexity of a Swiss watch with the structural
strength of a cantilever bridge. The ankle, it serves as
foundation, shock absorber and propulsion engine. The foot
can sustain enormous pressure - several tons over the course
of a one-mile run, for example - and still provide the
combination of flexibility and resiliency needed to support
delicate and demanding ballet steps.
The foot and ankle contain:
26 bones
33 joints
more than 100 muscles, tendons (fibrous tissues that
connect muscles to bones) and ligaments (fibrous tissues
connecting bones to other bones)
a vast network of blood vessels, nerves, skin and soft
tissue.
Together, the feet contain one-quarter of the bones in
the human body. All of these components work together in
unison to provide the body with support, balance and
mobility. A structural flaw or malfunction in any one part
can result in the development of problems elsewhere in the
body. Conversely, abnormalities in other parts of the body
ultimately can lead to problems in the feet.
Parts of the Foot
Structurally, the foot has three main parts; the forefoot,
the midfoot, and the hindfoot.
The
forefoot is composed of the five toes, collectively
called phalanges, and their connecting long bones, the
metatarsals. Each toe, or phalanx, is made up of
several small bones. The big toe, also called the
hallux, has two phalanges and two joints (interphalangeal
joints); it also features two tiny, round sesamoid
bones that enable it to move up and down. The other
four toes each have three bones and two joints. The
phalanges are connected to the metatarsals by five
metatarsal phalangeal joints at the ball of the foot.
Collectively, the forefoot bears half the body's
weight and balances pressure on the ball of the foot.
The
midfoot, featuring five irregularly shaped tarsal
bones, forms the foot's characteristic arch and serves
as a shock absorber. The bones of the midfoot are
connected to the forefoot and the hindfoot by muscles
and the plantar fascia or arch ligament.
The
hindfoot, composed of three joints, links the
midfoot to the ankle or talus. The top of the talus is
connected to the two long bones of the lower leg, the
tibia and fibula, forming a hinge that allows the foot
to move up and down. The heel bone or calcaneus, is the
largest bone of the foot. It joins the talus to form the
subtalar joint, which enables the foot to rotate at the
ankle. Its bottom is cushioned with a layer of fat.
Muscles, Tendons and Ligaments
Supporting this complex of bones and joints is a network
of muscles, tendons and ligaments.
There are some 20 muscles in the foot. They give the foot
its shape by holding the bones in position, and expand and
contract to impart movement to the bones and joints.
The
main muscles of the foot are:
the anterior tibial,
which enables the foot to move upward.
the posterior tibial, which
supports the arch.
the peroneal tibial, which
controls movement on the outside of the ankle
the extensors, which help
the ankle raise the toes and initiate the act of
stepping forward
the flexors, which help
stabilize the toes against the ground.
Other smaller muscles enable the toes to lift and curl.
In the foot there are elastic tissues that connect the
muscles to the bones and joints. The largest and strongest
tendon of the foot is the Achilles tendon, which extends
from the calf muscle of the leg to the heel. Its strength
and joint function facilitate running, jumping, walking up
stairs or raising the body onto the toes.
Ligaments hold the tendons in place and stabilize the
joints. The longest of these, the plantar fascia, forms the
arch on the sole of the foot from the heel to the toes. By
stretching and contracting, it allows the arch to curve or
flatten, providing balance and giving the foot strength to
push off and initiate the act of walking. Medial ligaments
on the inside and lateral ligaments on outside of the foot
provide stability and enable the foot to move up and down.
Skin, blood vessels and nerves help give the foot its
shape and durability, provide cell regeneration and
essential muscular nourishment, and control its many, varied
movements.
Here are some movies if you would like
to see the foot in action. Just click on them:
The foot and ankle contain:
The
forefoot is composed of the five toes, collectively
called phalanges, and their connecting long bones, the
metatarsals. Each toe, or phalanx, is made up of
several small bones. The big toe, also called the
hallux, has two phalanges and two joints (interphalangeal
joints); it also features two tiny, round sesamoid
bones that enable it to move up and down. The other
four toes each have three bones and two joints. The
phalanges are connected to the metatarsals by five
metatarsal phalangeal joints at the ball of the foot.
Collectively, the forefoot bears half the body's
weight and balances pressure on the ball of the foot.
The
midfoot, featuring five irregularly shaped tarsal
bones, forms the foot's characteristic arch and serves
as a shock absorber. The bones of the midfoot are
connected to the forefoot and the hindfoot by muscles
and the plantar fascia or arch ligament.
The
hindfoot, composed of three joints, links the
midfoot to the ankle or talus. The top of the talus is
connected to the two long bones of the lower leg, the
tibia and fibula, forming a hinge that allows the foot
to move up and down. The heel bone or calcaneus, is the
largest bone of the foot. It joins the talus to form the
subtalar joint, which enables the foot to rotate at the
ankle. Its bottom is cushioned with a layer of fat.
Supporting this complex of bones and joints is a network
of muscles, tendons and ligaments.
Ligaments hold the tendons in place and stabilize the
joints. The longest of these, the plantar fascia, forms the
arch on the sole of the foot from the heel to the toes. By
stretching and contracting, it allows the arch to curve or
flatten, providing balance and giving the foot strength to
push off and initiate the act of walking. Medial ligaments
on the inside and lateral ligaments on outside of the foot
provide stability and enable the foot to move up and down.