| CHRIS SERVANT |
| KNEE REPLACEMENT |
Why are knee replacements performed? |
| The major reason for having a joint replacement is to relieve the pain that is caused by arthritis.
The commonest form of arthritis is osteoarthritis, which is due to gradual wear and tear of the joint over the years.
Arthritis can also be due to inflammatory diseases such as rheumatoid arthritis or gout. |
| When the joint surfaces become worn they no longer glide smoothly against each other
and the surfaces also lose their ability to cushion the knee. This can cause pain, swelling and a grinding or
clicking feeling, usually made worse by activity. This can badly affect the quality of life, limiting your ability
to take part in recreational activities, exercise and even simple things such as going to the shops.
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| As time goes on the joint surfaces wear down so much that the underlying bone becomes
exposed and bare bone rubs on bare bone. One side of the knee can wear more than the other and this can lead to the
knee curving inwards or outwards (so that you become bow-legged or knock-kneed). The knee often then deteriorates
rapidly.
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More information on osteoarthritis (also known as degenerative arthritis) |
| Osteoarthritis is very common and results from wear of the normally smooth surfaces of
the joint. In the knee arthritis can result from injury but usually it is part of the normal aging process. |
| The normal joint surface is made of articular cartilage, which is a smooth but slightly spongy layer
(like the inside of a coconut), and is bathed in a fluid that allows very low friction movement.
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| On an X-ray a normal joint will appear to have a space between the two opposing joint surfaces.
This "joint space" is actually not a space at all, but the area occupied by the cartilage (cartilage does not show up
on X-rays). When the articular cartilage wears down an X-ray may show narrowing of the "joint space". Loss of the smooth
cartilage surface increases wear as the two rough surfaces move against each other like sandpaper, and this can cause pain
and inflammation in the joint (arthritis). Eventually one can have complete loss of the cartilage with bone rubbing
on bone. |
| A further sign of arthritis in the joint is the formation of "osteophytes". These are
extra spurs of bone that the body forms in an attempt to increase the area of the joint and thus decrease the load
across the joint. |
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X-ray of an arthritic knee |
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