261
CHAPTER EIGHT
Joints of the Skeletal System
DO GLUCOSAMINE AND CHONDROITIN HELP ARTHRITIS PAIN?
chondroitin did not improve arthritis symptoms any more than the placebo; the
people taking the drug improved somewhat. However, when the researchers
considered only those participants with moderate to severe arthritis, the dietary
supplements (alone or in combination) did alleviate pain, although not as fast
as the drug.
In a three-year study reported in 2001, people with knee arthritis taking
the placebo had narrowing of the joint space, whereas participants taking glu-
cosamine did not. Yet a two-year study published in 2008 on 222 people with
hip arthritis showed that glucosamine worked only as well as the placebo in alle-
viating pain and stalling joint narrowing in that aF
ected joint.
Two large ongoing clinical trials will add to the continuing evaluation of
these popular dietary supplements. One investigation is assessing biochemi-
cal evidence of cartilage breakdown, so may provide more definitive results.
Meanwhile, it is best to consult a physician before using glucosamine/chondroi-
tin to alleviate the pain of arthritis. Many people report that the supplements
help, and they have been studied enough to indicate that they seem safe, but
they usually take two to three months to be eF
ective—and we still do not know
exactly what they do to our joints.
G
lucosamine and chondroitin are widely sold as “dietary sup-
plements“ to treat the joint pain and joint space narrowing of
osteoarthritis. Anecdotal reports and many small studies indi-
cate that these supplements are eF
ective, but large, controlled
clinical trials have yielded con±
icting and confusing results.
Glucosamine and chondroitin are carbohydrates produced in the
body, but in dietary supplements come from shells and cow cartilage,
respectively. The recommended dose is 1,500 milligrams of glucosamine
a day and 1,200 milligrams of chondroitin, usually taken in combined form
two or three times a day. Dosages may be uneven, however, because these
biochemicals are marketed as dietary supplements and not drugs, which
are more precisely regulated.
The largest study completed so far is GAIT (Glucosamine/Chondroitin
Arthritis Intervention Trial). Run by the Veterans Administration and the
National Institutes of Health with results published in 2006, GAIT random-
ized 1,583 people with osteoarthritis of the knee into ²
ve treatment groups:
glucosamine alone, chondroitin alone, glucosamine and chondroitin, cele-
coxib (a drug), and placebo. After tweny-four weeks, glucosamine and/or
8.1
INTRODUCTION
Joints, or
articulations
(ar-tik
u-la
shunz), are functional
junctions between bones. They bind parts of the skeletal sys-
tem, make possible bone growth, permit parts of the skel-
eton to change shape during childbirth, and enable the body
to move in response to skeletal muscle contractions.
8.2
CLASSIFICATION OF JOINTS
Joints vary considerably in structure and function. However,
they can be classiF
ed by the type of tissue that binds the
bones at each junction. Three general groups are fibrous
joints, cartilaginous joints, and synovial joints.
Joints can also be grouped according to the degree of
movement possible at the bony junctions. In this scheme,
joints are classified as immovable (synarthrotic), slightly
movable (amphiarthrotic), and freely movable (diarthrotic).
At some diarthrotic joints, movement can occur over con-
siderable distances, such as flexion and extension of the
elbow. Whereas other, such as the joint between the sac-
crum and the ilium, move freely, but only for a short dis-
tance. The structural and functional classiF cation schemes
overlap somewhat. Currently, structural classiF cation is the
one most commonly used.
Fibrous Joints
Fibrous
(F
brus)
joints
are so named because the dense con-
nective tissue holding them together includes many collage-
nous F bers. These joints are between bones in close contact.
The three types of F
brous joints are
1.
Syndesmosis
(sin
des-mo
sis). In this type of joint, the
bones are bound by a sheet (
interosseous membrane
)
or bundle of dense connective tissue (
interosseous
ligament
)
.
This junction is fl
exible and may be twisted,
so the joint may permit slight movement and thus is
amphiarthrotic (am
fe-ar-thro
tik). A syndesmosis lies
between the tibia and F
bula
(f
g. 8.1)
.
2.
Suture
(soo
cher). Sutures are only between fl
at bones
of the skull, where the broad margins of adjacent
bones grow together and unite by a thin layer of dense
Fibula
Interosseus
membrane
of leg
Tibia
Medial
malleolus
Anterior
tibiofibular
ligament
(interosseus
ligament)
Lateral
malleolus
FIGURE 8.1
The articulation between the tibia and ²
bula is an
example of a syndesmosis.
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