Knee replacement • Figure 5.18
In a surgical procedure called arthroplasty, an injured knee is replaced
surgically with an artificial one.
Patellar surface
removed
a.
Preparation for total knee replacement
Patellar component
Plastic spacer
Femoral component
Tibial component
b.
Components of artificial knee joint prior to implantation
Femur
Femoral
component
Tibial
component
Tibia
Patellar
component
c. Implanted components of a total knee replacement
Arthritis Develops In Joints Due
to Wear and Tear
Joints also show wear and tear with age. The following
changes in joints occur as you get older:
Arthroscopic view of a knee
whose medial meniscus show
signs of degeneration
ple show signs of degeneration in the knees (Figure 5.18),
elbows, hips, shoulders, and even the vertebral column.
A degenerative joint disease associated with aging is
called osteoarthritis (
os'-te-o-ar-THR
l
-tis
). In this con-
dition, the joint cartilage deteriorates because with use,
the cartilage thins. As the cartilage disappears from the
joint, the bone surfaces have more friction, which leads
to irritation and inflammation of joints, muscle weak-
ness, and further wear and abrasion. Osteoarthritis is the
most common type of arthritis.
Osteoarthritis may be treated by
injecting hyaluronic acid into the
affected joint to improve lubrication. Severe osteoarthritis
may require surgery to replace the degenerated joint with
an artificial one, such as a knee replacement (see Figure
5.18) or hip replacement. Knee and hip replacements are
usually accompanied by months of physical therapy to en-
sure that the patient regains normal mobility.
A second type of arthritis, rheumatoid arthritis, also
leads to deterioration of the joint surfaces. This condition
is caused by an abnormal reaction of the immune system
known as autoimmunity. The immune system appears to
attack the tissues of the joint, causing deterioration and
inflammation of the articulation. Unlike osteoarthritis,
rheumatoid arthritis tends to be a disease condition that
starts at a much younger age (often in the teens).
arthritis
(ar-THRI-tis)
Inflammation of a joint.
Synovial joints decrease production of synovial fluid.
Cartilage becomes thinner and worn.
Ligaments shorten and become less flexible.
The result is pain, swelling, and loss of mobility. Age-related
changes can begin as early as age 20, and by age 80 most peo-
CONCEPT CHECK
1.
What
are the two major effects of aging on
bone?
2.
What
happens to joints as they age?
Skeletal Structure Changes with Aging 145
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