Essentials of Anatomy and Physiology

130

Bone

Synovial

membrane

Joint

capsule

Joint cavity

(synovial fluid)

Bursa

Articular

cartilage

Tendon

Bone

Figure 6–16. Structure of a synovial joint. See

text for description.

QUESTION:How can you tell that this is a joint

between two long bones? Give an example.

BOX6–5 ARTHRITIS

bacterial and viral infections have been suggested

as possibilities.

Rheumatoid arthritis often begins in joints of the

extremities, such as those of the fingers. The

autoimmune activity seems to affect the synovial

membrane, and joints become painful and stiff.

Sometimes the disease progresses to total destruc-

tion of the synovial membrane and calcification of

the joint. Such a joint is then fused and has no

mobility at all. Autoimmune damage may also

occur in the heart and blood vessels, and those with

RA are more prone to heart attacks and strokes (RA

is a systemic, not a localized, disease).

Treatment of rheumatoid arthritis is directed at

reducing inflammation as much as possible, for it is

the inflammatory process that causes the damage.

Therapies being investigated involve selectively

blocking specific aspects of the immune response,

such as antibody production. At present there is no

cure for autoimmune diseases.

The term arthritis means “inflammation of a

joint.” Of the many types of arthritis, we will con-

sider two: osteoarthritis and rheumatoid arthritis.

Osteoarthritisis a natural consequence of get-

ting older. In joints that have borne weight for

many years, the articular cartilage is gradually worn

away. The once smooth joint surface becomes

rough, and the affected joint is stiff and painful. As

you might guess, the large, weight-bearing joints

are most often subjected to this form of arthritis. If

we live long enough, most of us can expect some

osteoarthritis in knees, hips, or ankles.

Rheumatoid arthritis(RA) can be a truly crip-

pling disease that may begin in early middle age

or, less commonly, during adolescence. It is an

autoimmune disease, which means that the

immune system mistakenly directs its destructive

capability against part of the body. Exactly what

triggers this abnormal response by the immune

system is not known with certainty, but certain