280
UNIT TWO
cartilage. In the intervertebral discs, less water diminishes
the fl
exibility of the vertebral column and impairs the ability
of the soft centers of the discs to absorb shocks. The discs
may even collapse on themselves slightly, contributing to
the loss of height in the elderly. The stiffening spine gradu-
ally restricts the range of motion.
Loss of function in synovial joints begins in the third
decade of life, but progresses slowly. Fewer capillaries serv-
ing the synovial membrane slows the circulation of synovial
uid, and the membrane may become in±
ltrated with ±
brous
material and cartilage. As a result, the joint may lose elastic-
ity, stiffening. More collagen cross-links shorten and stiffen
ligaments, affecting the range of motion. This may, in turn,
upset balance and retard the ability to respond in a protec-
tive way to falling, which may explain why older people are
more likely to be injured in a fall than younger individuals.
Using joints, through activity and exercise, can keep
them functional longer. Disuse hampers the blood supply
to joints, which hastens stiffening. Paradoxically, this can
keep people from exercising, when this is exactly what they
should be doing.
PRACTICE
21
Which type of joint is the F
rst to show signs of aging?
22
Describe the loss of function in synovial joints as a progressive
process.
FIGURE 8.23
Nuclear scan of (
a
) a healthy knee and (
b
) an arthritic knee. The di±
erent colors in (
b
) indicate changes within the tissues associated
with degeneration.
(a)
(b)
FIGURE 8.22
Arthroscopic view of a torn meniscus in the knee and
arthroscopic scissors. ²ibrocartilage does not heal well, so in many
cases of torn meniscus the only treatment option is to cut out the
damaged portion.
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