Arthritis

Most of our joints are hinge like structures where two bones meet to
allow motion. Bones rubbing against one another do not wear well and
with time deform and cause pain. Fortunately, our joints have a
remarkable substance covering these bones called articular cartilage.
This cartilage has no nerve endings, so we don't feel pain. Cartilage
and can last for years with little signs of wear, however, when it
wears out, it is gone. Our bodies do not regenerate articular
cartilage. With all of our technology, medical science still cannot
regenerate articular cartilage in a joint.

X-ray of normal knee (left) and knee with arthritis (right). Notice the
loss
of joint space with bone touching bone.