278
UNIT TWO
Tearing or displacing a meniscus is a common knee injury, usually
resulting from forcefully twisting the knee when the leg is F
exed
g.
8.22)
. The meniscus is composed of ±
brocartilage, so this type of injury
heals slowly. Also, a torn and displaced portion of cartilage jammed
between the articulating surfaces impedes movement of the joint.
²ollowing such a knee injury, the synovial membrane may become
inF
amed (acute synovitis) and secrete excess F
uid, distending the joint
capsule so that the knee swells above and on the sides of the patella.
ferent types of arthritis a³
ect 50 million people
in the United States. Arthritis can also be part of
other syndromes (table 8A). The most common
types of arthritis are rheumatoid arthritis (RA),
osteoarthritis, and Lyme arthritis.
Rheumatoid Arthritis (RA)
Rheumatoid arthritis, an autoimmune disor-
der (a condition in which the immune system
attacks the body’s healthy tissues), is painful and
debilitating. The synovial membrane of a joint
becomes inF
amed and thickens, forming a mass
called a pannus. Then, the articular cartilage is
damaged, and ±
brous tissue in±
ltrates, interfer-
ing with joint movements. In time, the joint may
ossify, fusing the articulating bones (bony anky-
losis). Joints severely damaged by RA may be sur-
gically replaced.
RA may affect many joints or only a few.
It is usually a systemic illness, accompanied by
fatigue, muscular atrophy, anemia, and osteopo-
rosis, as well as changes in the skin, eyes, lungs,
blood vessels, and heart. RA usually a³
ects adults,
but there is a juvenile form.
Osteoarthritis
Osteoarthritis, a degenerative disorder, is the
most common type of arthritis (fig. 8A). It usu-
ally occurs with aging, but an inherited form may
appear as early as one’s thirties. A person may
±
rst become aware of osteoarthritis when a blow
to the affected joint produces pain much more
intense than normal. Gradually, the area of the
ected joint deforms. Arthritic ±
ngers take on a
gnarled appearance, or a knee may bulge.
In osteoarthritis, articular cartilage softens
and disintegrates gradually, roughening the
articular surfaces. Joints become painful, with
restricted movement. ²or example, arthritic ±
n-
gers may lock into place while a person is playing
J
oints have a tough job. They must support
weight, provide a great variety of body
movements, and are used frequently. In
addition to this normal wear and tear, these struc-
tures are sometimes subjected to injury from
trauma, overuse, infection, a misplaced immune
system attack, or degeneration. Here is a look at
some common joint problems.
Sprains
Sprains
result from overstretching or tearing the
connective tissues, including cartilage, ligaments,
and tendons, associated with a joint, but they do
not dislocate the articular bones. Usually forceful
wrenching or twisting sprains the wrist or ankles.
²or example, inverting an ankle too far can sprain
it by stretching the ligaments on its lateral sur-
face. Severe injuries may pull these tissues loose
from their attachments.
A sprained joint is painful and swollen,
restricting movement. Immediate treatment of
a sprain is rest; more serious cases require medi-
cal attention. However, immobilization of a joint,
even for a brief period, causes bone resorption
and weakens ligaments. Consequently, exercise
may help strengthen the joint.
Bursitis
Overuse of a joint or stress on a bursa may cause
bursitis
,
an inflammation of a bursa. The bursa
between the heel bone (calcaneus) and the
Achilles tendon may become inF
amed as a result
of a sudden increase in physical activity using
the feet. Similarly, a form of bursitis called tennis
elbow a³
ects the bursa between the olecranon
process and the skin. Bursitis is treated with rest.
Medical attention may be necessary.
Arthritis
Arthritis
is a disease that causes inF
amed, swol-
len, and painful joints. More than a hundred dif-
the guitar or tying a shoelace. Osteoarthritis most
often a³
ects joints used the most over a lifetime,
such as those of the ±
ngers, hips, knees, and the
lower parts of the vertebral column.
Nonsteroidal anti-inflammatory drugs
(NSAIDs) have been used for many years to con-
trol osteoarthritis symptoms. NSAIDs called
COX-2 inhibitors relieve inflammation without
the gastrointestinal side effects of older drugs,
but they are prescribed only to people who do
not have risk factors for cardiovascular disease,
to which some of these drugs are linked. The
COX-2 inhibitors are generally not more e³
ective
at relieving joint pain than other NSAIDs. Exercise
can keep osteoarthritic joints more F
exible.
Lyme Arthritis
Lyme disease, a bacterial infection passed in a tick
bite, causes intermittent arthritis of several joints,
usually weeks after the initial symptoms of rash,
fatigue, and F
ulike aches and pains. Lyme arthritis
was ±
rst observed in Lyme, Connecticut, where an
astute woman kept a journal after noticing that
many of her young neighbors had what appeared
to be the very rare juvenile form of rheumatoid
arthritis. Her observations led Allen Steere, a Yale
University rheumatologist, to trace the illness to
a tick-borne bacterial infection. Antibiotic treat-
ment beginning as soon as the early symptoms of
Lyme disease are recognized can prevent devel-
opment of the associated arthritis.
Other types of bacteria that cause arthri-
tis include common
Staphylococcus
and
Streptococcus
species,
Neisseria gonorrhoeae
(which causes the sexually transmitted disease
gonorrhea), and
Mycobacterium
(which causes
tuberculosis). Arthritis may also be associated
with AIDS, because the immune system break-
down raises the risk of infection by bacteria that
can cause arthritis.
8.2
CLINICAL APPLICATION
Joint Disorders
8.7
LIFE-SPAN CHANGES
Joint stiffness is an early sign of aging. By the fourth decade,
a person may notice that the first steps each morning
become difF
cult. Changes in collagen structure lie behind the
increasing stiffness
(f g. 8.23)
. Range of motion may dimin-
ish. However, joints age slowly, and exercise can lessen or
forestall stiffness.
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