The foot as a functional unit pdf - Lower limb

508

CHAPTER 10

third, as in the hand.

take place from the midline of the second digit and not the

toes, performed by the interossei muscles, are minimal and

The movements of abduction and adduction of the

verse ligaments connect the joints of the five toes.

resemble those of the hand (see page 412). The deep trans

The metatarsophalangeal and interphalangeal joints closely

sal joint of the big toe has a separate joint cavity.

sal, plantar, and interosseous ligaments. The tarsometatar

joints of the plane variety. The bones are connected by dor

The tarsometatarsal and intermetatarsal joints are synovial

Tarsometatarsal and Intermetatarsal

ligaments.

bones are connected by dorsal, plantar, and interosseous

continuous with that of the cuneonavicular joint. The

vial joints of the plane variety. Their joint cavities are

The intercuneiform and cuneocuboid joints are syno

Intercuneiform and Cuneocuboid Joints

ous ligaments.

the two bones connected by dorsal, plantar, and interosse

The cuboideonavicular joint is usually a fibrous joint, with

Cuboideonavicular Joint

The Lower Limb

Joints

-
-

Metatarsophalangeal and

Interphalangeal Joints

Later, osteoarthritic changes occur in the metatarsophalan

which is a lateral deviation of the great toe

Metatarsophalangeal Joint of the Big Toe

Hallux valgus,

at the metatarsophalangeal joint, is a common condition. Its

incidence is greater in women than in men and is associated

with badly fitting shoes. It is often accompanied by the pres-

ence of a short 1st metatarsal bone. Once the deformity is

established, it is progressively worsened by the pull of the

flexor hallucis longus and extensor hallucis longus muscles.

geal joint, which then becomes stiff and painful; the condition

is then known as hallux rigidus.

C L I N I C A L N O T E S

The Foot as a Functional Unit

assist the forward propulsive action of the gastrocnemius

and toes (i.e., the takeoff point of the foot) and greatly

exert their action on the bones of the forepart of the foot

long flexor muscles and the small muscles of the foot can

able and can adapt itself to uneven surfaces. Moreover, the

the lever is segmented with multiple joints, the foot is pli

activities of the gastrocnemius and soleus muscles. Because

forward propulsive action would depend entirely on the

the foot could not adapt itself to uneven surfaces, and the

pulsion (Fig. 10.66). However, with such an arrangement,

body weight and serve well as a rigid lever for forward pro

bone instead of a series of small bones, it could sustain the

walking and running. If the foot possessed a single strong

weight and to serve as a lever to propel the body forward in

The foot has two important functions: to support the body

The Foot as a Weight Bearer

and a Lever

and soleus muscles (Fig. 10.66).

the following engineering methods used for its support

Examination of the design of any stone bridge reveals

Mechanisms of Arch Support

bones (Fig. 10.67).

atarsal bones and the cuboid and the three cuneiform

This consists of the bases of the met

Transverse arch:

(Fig. 10.67).

neum, the cuboid, and the 4th and 5th metatarsal bones

This consists of the calca

Lateral longitudinal arch:

bones, and the first three metatarsal bones (Fig. 10.63).

neum, the talus, the navicular bone, the three cuneiform

This consists of the calca

Medial longitudinal arch:

graph of the foot shows the bones that form the arches.

An examination of an articulated foot or a lateral radio

The Bones of the Arches

metatarsals.

of the first metatarsal and the heads of the remaining four

in front, namely, the two sesamoid bones under the head

the heel behind and six points of contact with the ground

body weight on standing is distributed through a foot via

From this description, it can be understood that the

the two feet are placed together, a complete dome is formed.

likened to a half-dome, so that when the medial borders of

its summit on the foot’s medial border. The foot has been

an arch, with its base on the lateral border of the foot and

the cuboid and cuneiform bones. This is, in fact, only half

transverse arch involves the bases of the five metatarsals and

the presence of the low-lying lateral longitudinal arch. The

5th metatarsal head and least between these areas because of

the lateral margin of the foot is greatest at the heel and the

longitudinal arch. The pressure exerted on the ground by

arched above the ground because of the important medial

gin of the foot, from the heel to the 1st metatarsal head, is

are in contact with the ground (Fig. 10.67). The medial mar

the metatarsal heads, and the pads of the distal phalanges

that the heel, the lateral margin of the foot, the pad under

made with the person in the standing position, one can see

On examination of the imprint of a wet foot on the floor

a large amount of subcutaneous fat on the sole of the foot.

child, the foot appears to be flat because of the presence of

(Fig. 10.67). In the young

transverse arches

and

medial longitudinal, lateral longi

are present at birth: the

in the form of an arch. The foot has three such arches, which

A segmented structure can hold up weight only if it is built

The Arches of the Foot

tudinal,

■

(Fig. 10.68):

with the thin edge of the wedge lying inferiorly. This

porting the arch is to make the stones wedge shaped,

The most effective way of sup

The shape of the stones:

■

Basic Anatomy

The cuboid is the keystone.

of the calcaneum and the proximal end of the cuboid.

Minimal shaping of the distal end

Shape of the bones:

Maintenance of the Lateral Longitudinal Arch

and posterior and the medial ligament of the ankle joint.

are the tibialis anterior

Suspending the arch from above

flexor hallucis brevis (Fig. 10.68).

the medial part of the flexor digitorum longus, and the

brevis, the abductor hallucis, the flexor hallucis longus,

aponeurosis, the medial part of the flexor digitorum

are the plantar

Tying the ends of the arch together

terior muscle play an important role in this respect.

tendinous extensions of the insertion of the tibialis pos

the plantar calcaneonavicular ligament (Fig. 10.68). The

the dorsal ligaments. The most important ligament is

plantar ligaments, which are larger and stronger than

by the

The inferior edges of the bones are tied together

the keystone in the center of the arch (Fig. 10.68).

receives the navicular. The rounded head of the talus is

ity of the proximal surface of the medial cuneiform bone

receives the rounded head of the talus; the slight concav

talus; the concave proximal surface of the navicular bone

The sustentaculum tali holds up the

Shape of the bones:

Maintenance of the Medial Longitudinal Arch

ods used to support the arches of the feet (Fig. 10.68).

Using the bridge analogy, one can now examine the meth

a cable above the level of the bridge.

depends on multiple supports suspending the arch from

Here, the maintenance of the arch

A suspension bridge:

ration of the pillars and consequent sagging of the arch.

tie beam connecting the ends effectively prevents sepa

is large and the foundations at either end are insecure, a

When the span of the bridge

The use of the tie beams:

bearing.

edges of the stones to separate when the arch is weight

method effectively counteracts the tendency of the lower

ing their lower edges together with metal staples. This

is accomplished by interlocking the stones or bind

This

The inferior edges of the stones are tied together:

the center of the arch and is referred to as the “keystone.”

applies particularly to the important stone that occupies

509

■

gastrocnemius, soleus,
and plantaris

flexor hallucis
longus and
flexor digitorum
longus

A segmented lever

A simple lever

print of normal foot

print of flat foot

FIGURE 10.66

The foot as a simple lever

shown.

. Floor prints of a normal foot and a flat foot are also

and as a segmented lever

(A)

(B)

sesamoid bone

first metatarsal

medial cuneiform

navicular

talus

sustentaculum tali

calcaneum

fifth metatarsal

lateral longitudinal arch

bases of metatarsal bones

intermediate cuneiform

lateral cuneiform

cuboid

medial cuneiform

transverse arch

cuboid

medial longitudinal arch

FIGURE 10.67

Bones forming the medial longitudinal, lateral longitudinal, and transverse arches of the right foot.

510

CHAPTER 10

training to develop their muscle tone.

sustain their arches provided that they receive adequate

Athletes, route-marching soldiers, and nurses are able to

ligaments of the feet and results in fallen arches or flat feet.

son is overweight, places excessive strain on the bones and

Standing immobile for long periods, especially if the per

ing walking and running, all these muscles become active.

arches. They are commonly totally inactive. However, dur

play no important role in the normal static support of the

the peroneus longus, and the small muscles of the foot

onstrated electromyographically that the tibialis anterior,

factors is the most important? Basmajian and Stecko dem

bones, strong ligaments, and muscle tone. Which of these

The arches of the feet are maintained by the shape of the

gus tendon and the peroneus brevis.

are the peroneus lon

Suspending the arch from above

longus tendon.

is the peroneus

Tying the ends of the arch together

this respect.

of the adductor hallucis are particularly important in

of the foot; the dorsal interossei and the transverse head

and the origins of the plantar muscles from the forepart

deep transverse ligaments, the strong plantar ligaments,

by the

The inferior edges of the bones are tied together

(Fig. 10.67).

cuneiform bones and the bases of the metatarsal bones

The marked wedge shaping of the

Shape of the bones:

Maintenance of the Transverse Arch

gus and the brevis (Fig. 10.68).

are the peroneus lon

Suspending the arch from above

part of the flexor digitorum longus and brevis.

aponeurosis, the abductor digiti minimi, and the lateral

are the plantar

Tying the ends of the arch together

short muscles from the forepart of the foot (Fig. 10.68).

long and short plantar ligaments and the origins of the

by the

The inferior edges of the bones are tied together

The Lower Limb

■

keystone

shape of stones

shape of bones

staples

short plantar ligament

long plantar ligament

calcaneonavicular ligament

strong plantar ligaments

tendon of flexor
hallucis longus

tie beam

peroneus longus

suspension bridge

tendon of flexor
hallucis longus

peroneus longus

FIGURE 10.68

Different methods by which the arches of the foot may be supported.

Basic Anatomy

511

Clinical Problems Associated with the Arches of the Foot

nal arch is unduly high. Most cases are caused by muscle imbal

(clawfoot) is a condition in which the medial longitudi

Pes cavus

tendons are also permanently stretched. The causes of flat foot

vicular, and medial ligaments of the ankle joint become perma

the deformity has existed for some time, the plantar, calcaneona

muscular support gives way, the ligaments are stretched, and

periods (waitress or nurse), by overweight, or by illness, the

(a long-route march by an army recruit), by standing for long

port. When the muscles are fatigued by excessive exercise

foot the tone of muscles is an important factor in arch sup

supporting the arches. It has been shown that in the active

the foot, and the tone of muscles all play an important role in

strong ligaments, especially those on the plantar surface of

clinically the most important. The shape of the bones, the

Of the three arches, the medial longitudinal is the largest and

pain is produced.

Pes planus (flat foot) is a condition in which the medial longi-

tudinal arch is depressed or collapsed. As a result, the forefoot

is displaced laterally and everted. The head of the talus is no

longer supported, and the body weight forces it downward and

medially between the calcaneum and the navicular bone. When

nently stretched, and the bones change shape. The muscles and

are both congenital and acquired.

ance, in many instances resulting from poliomyelitis.

C L I N I C A L N O T E S

The Propulsive Action of the Foot

up, thereby increasing their efficiency. The body is then

nal arches. The “slack” in the long flexor tendons is taken

shortening the tie beams and heightening the longitudi

joints, and the plantar aponeurosis is pulled on, thus

rises, the toes are extended at the metatarsophalangeal

foot and the heads of the metatarsal bones. As the heel

weight is borne successively on the lateral margin of the

As the body weight is thrown forward, the

Walking

first metatarsal).

(including the two sesamoid bones under the head of the

heel behind and the heads of the metatarsal bones in front

The body weight is distributed via the

Standing Immobile

Bursae and Bursitis in the Lower Limb

times develops over the tendo calcaneus in response to badly

excessive friction. For example, a subcutaneous bursa some

sus muscle, may enlarge in patients with osteoarthritis of the

the patella beneath the quadriceps femoris muscle. The bursa,

bursa extends proximally about three fingerbreadths above

synovial fluid accumulate within the joint. The suprapatellar

and they can become distended if excessive amounts of

Two important bursae communicate with the knee joint,

neum (long-distance runner’s ankle).

A variety of bursae are found in the lower limb where skin, ten-

dons, ligaments, or muscles repeatedly rub against bony points

or ridges.

Bursitis, or inflammation of a bursa, can be caused by acute

or chronic trauma, crystal disease, infection, or disease of a

neighboring joint that communicates with the bursa. An inflamed

bursa becomes distended with excessive amounts of fluid. The

following bursae are prone to inflammation: the bursa over the

ischial tuberosity; the greater trochanter bursa; the prepatellar

and superficial infrapatellar bursae; the bursa between the ten-

dons of insertion of the sartorius, gracilis, and semitendinosus

muscles on the medial proximal aspect of the tibia; and the bursa

between the tendo calcaneus and the upper part of the calca-

which is associated with the insertion of the semimembrano-

knee joint.

The anatomic bursae described should not be confused with

adventitious bursae, which develop in response to abnormal and

fitting shoes. A bunion is an adventitial bursa located over the

medial side of the head of the 1st metatarsal bone.

C L I N I C A L N O T E S

thrown forward by the actions of the gastrocnemius and

mechanisms described for walking (above).

ground. The forward thrust to the body is provided by the

the forepart of the foot, and the heel does not touch the

When a person runs, the weight is borne on

Running

ing the ankle joint.

action, the long flexor tendons also assist in plantar flex

of the strong action of the flexor digitorum longus. In this

the toes extended so that they do not fold under because

forward. The lumbricals and interossei contract and keep

and short flexors of the foot, providing the final thrust

a lever, and by the toes being strongly flexed by the long

soleus (and plantaris) on the ankle joint, using the foot as