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« An x-ray of a normal knee »
Related topic >
Knee anatomy
When people talk about knee arthritis they are usually referring to
osteoarthritis or “wear and tear” damage to the knee.
It is important to remember that knee arthritis is also a term used
for some inflammatory diseases of the joint which can also cause knee
pain and a similar end result. One example of this type of arthritis
is rheumatoid arthritis.
The underlying process in knee osteoarthritis, which may eventually
cause severe pain, is of damage and complete wearing out of the articular
cartilage (joint surface) in any part of the knee joint.
This results in bone grinding on bone in the knee
which is a painful and disabling condition.
Any of the three main parts of the knee (the medial compartment, the
lateral compartment, and the patello-femoral joint) can be affected
by knee osteoarthritis. One or more parts of the knee may be affected
at any one time, but the commonest site for knee arthritis affecting
a single compartment is in the medial (inner) compartment.
Knee Osteoarthritis may arise when there has been no previous story
of injury or damage to the knee. Sometimes it gradually comes on after
an initial injury to the articular cartilage of the knee, and it is
well known that having a torn cartilage does increase the risk of
developing knee osteoarthritis later in life.
« A diagram of an osteoarthritic knee »
« An x-ray of knee osteoarthritis »
The predominant symptom of knee osteoarthritis pain of varying degree.
This can be felt as a relatively mild background ache in the knee
which might interfere, for example, with sporting activities or a
long walk, right up to constant severe disabling pain which makes
walking very difficult or impossible. Knee osteoarthritis may also
be so severe that sleep can be disturbed and there is pain at rest.
The normal activities of daily living may become difficult to perform
because of knee osteoarthritis.
Sometimes, because of the roughening of the knee joint surface, there
may be catching, clicking, clunking or similar symptoms as well as
pain. In more severe cases of knee osteoarthritis these are less significant
than the underlying pain.
Swelling of the knee joint is often seen.
A tear of a so called 'degenerate cartilage' can often be found in
the knee with osteoarthritic.
The diagnosis of osteoarthritis of the knee can be made from the typical
symptoms of this condition along with examination.
Anybody who has suspected knee osteoarthritis will usually have an
x-ray of the knee taken which will confirm the diagnosis.
If you have osteoarthritis of the knee you may well have undertaken
some form of treatment before coming to see a knee surgeon. These
non-surgical means of knee osteoarthritis treatment include simple
pain killers, anti-inflammatory tablets, injections of cortisone or
other substances, advice about weight loss, modification of activities
and physiotherapy. Physiotherapy may include a whole range of associated
treatments and might also result in advice about using a walking stick
etc.
If the suspicion is of an early degree of knee arthritis and/or you
are relatively young, it may be appropriate to have an arthroscopy
of the knee. This will improve some of the mechanical symptoms arising
from the knee, give some temporary relief by washing out the irritating
debris within the knee, and define the exact problem with a view to
later major surgery. However, knee arthroscopy treatment cannot
reverse the damage or cure knee osteoarthritis itself.
Eventually the decision might be made between yourself and your surgeon,
that the pain has reached the point where the only option is knee
arthroplasty. Knee arthroplasty is a general term for knee
replacement. Knee replacement may take the form of a total
knee replacement or a partial (unicompartmental) knee replacement.
Total knee replacement involves the resurfacing of the worn out parts
of the knee using a metal component on the end of the femur and the
top of the tibia, with a plastic bearing in between. Some surgeons
also put a plastic component on the back of the kneecap. The way in
which a knee replacement relieves pain is simply by removing the source
of the pain which is the bone grinding on bone; the knee lining is
effectively resurfaced.
« A diagram of a total knee replacement
»
« An x-ray of a total knee replacement
»
A total knee replacement operation usually takes places under a general
or spinal anaesthetic. The final decision about this is down to the
anaesthetist.
There will be an incision down the front of the knee. Total knee replacement
surgery itself takes approximately one hour.
When you wake up you will find that there is a firm bandage around
the knee and sometimes a light splint will be applied for comfort.
Depending upon the anaesthetist, you may have had injections into
the nerves which supply feeling to the lower leg. This is called a
regional nerve block and the aim is to achieve some
post operative pain relief.
There may also be one or two small tubes coming out through the skin
in the thigh. These are called drains. The aim of a drain is to remove
some of the blood which unavoidably collects within the knee after
surgery. During total knee replacement surgery there is little or
no bleeding because most operations for knee replacement are done
with a tourniquet applied to the upper thigh.
Rehabilitation and physiotherapy will usually commence the day after
total knee replacement surgery.
(related topic >
physiotherapy)
For a total knee replacement, the average length of stay in hospital
is approximately 5 days. If you have had removable stitches or metal
skin clips put into the skin these will be removed at between 10 and
12 days after total knee replacement surgery. If you have had dissolving
stitches put in the skin these do not require removal.
Physiotherapy after total knee replacement will often continue on
an outpatient basis until you have made an appropriate recovery and
your surgeon will give you a check up appointment 6 to 8 weeks from
total knee replacement surgery.
One of the things to remember about total knee replacement is that,
although the most rapid recovery takes place over the first weeks,
it can take at least 6 months for a knee replacement to get to its
best.
Severe pain is the main reason for having a total knee replacement.
Associated problems such as deformity of the knee because of the arthritis
(e.g. bow legs) and reduction in function, will improve following
knee replacement but in themselves are not a reason for having the
operation.
There is no operation which does not carry some risks.
The main risks of total knee replacement are:
Infection (the chances of a serious deep infection
affecting a total knee replacement are approximately 1%, although
up to 2-3% may develop a simple wound infection).
Deep venous thrombosis (DVT, blood clots) affecting
the lower leg can occur but precautions are taken to reduce the chance
of this either in the form of blood thinning tablets or injections,
or special calf pumps to keep the blood flowing. Pulmonary embolism
(PE) is a rare but serious complication arising when a blood clot
obstructs some of the veins in the lungs.
Nerve damage can occur, but this is usually seen
in the form of a numb patch of skin to one side of the scar. It is
extremely rare to have nerve damage from a knee replacement causing
weakness in the leg or foot.
Stiffness: sometimes despite having a technically
successful operation, the knee can be stiffer than hoped for which
can result in aching and general dissatisfaction. It is not always
possible to work out a reason for this.
The above are some of the major and more commonly occurring early
risks from total knee replacement but your surgeon or physiotherapist
will discuss and answer any more specific questions with you.
On average, you have approximately a 95% chance of getting a good
result from a knee replacement, giving you pain relief for at least
10 years. It may eventually fail by wearing out or loosening, amongst
other things.
If your knee arthritis affects only one of the three major compartments
of the knee you may be suitable for a unicompartmental, sometimes
called a half knee replacement. The most usual site for this is the
medial (inner) compartment of the knee.
« A diagram of a uni-compartment knee replacement
»
« An x-ray of a uni-compartment knee replacement
»
Approximately 25% of patients with established knee arthritis may
be suitable for a medial unicompartmental replacement. There are some
theoretical and actual benefits of this procedure: the incision is
smaller, the length of stay in hospital is usually shorter and the
speed of rehabilitation is quicker. There is also some evidence that
patients who have had a medial unicompartmental knee replacement have
a knee which feels more “normal”.
There is no evidence that the long term survival of a unicompartmental
knee replacement is better or worse than a total knee replacement,
and the pain relief at a few months from surgery is similar.
In total knee replacement or unicompartmental knee replacement, the
plastic bearing which sits between the two metal components may be
fixed (a fixed bearing knee replacement) or mobile bearing total knee
replacement. A mobile bearing total knee replacement means that the
plastic is not fixed rigidly to the tibial component, and can move
around in a number of planes. Depending on the actual implant used
this movement may take place backwards and forwards, sideways, rotation
or a combination.
The benefits of these types of implants are still theoretical and
laboratory based, but the idea is that there may be a reduction in
the wear of the plastic and therefore the long term loosening. There
are also some claims that function and range of movement of the knee
may be improved. There is no solid evidence for this yet.
Whether you have a total knee replacement or unicompartmental knee
replacement, the smallest possible incision will be used which allows
safe and satisfactory implantation of the knee replacement.
You maybe aware of minimally invasive total knee replacements, put
in through small incisions using special instruments. Minimally invasive
total knee replacement is available for selected patients. There may
be a short term benefit with less post operative pain and quicker
recovery. There is no proof yet that minimally invasive total knee
replacement is a better procedure in the long term. Minimally invasive
total knee replacement is technically more difficult and there may
be some increased risks. Studies are being undertaken at the moment
to answer some of the questions.
It is fair to say that minimally invasive total knee replacement is
an evolving part of knee replacement surgery.
Arthritis affecting only the joint between the knee cap and femur
(the patello-femoral joint) may be suitable for patello-femoral resurfacing.
In patello-femoral resurfacing a plastic component is put on the back
of the knee cap and a metal component on the front of the femur leaving
the main knee joint between the tibia and the femur alone. Patello-femoral
resurfacing is a relatively new technique compared to total knee replacement,
but is successful in patients who have a certain type of osteoarthritis
and your surgeon may discuss this with you.
« An image of a patello-femoral replacement
»
High tibial osteotomy (HTO) involves the cutting of the tibia just
below the knee joint to realign it. In cases of medial compartment
osteoarthritis which is not too severe, and affecting relatively young
active patients, it may be considered by your surgeon.
In such patients the benefits of HTO are that if successful and once
a full recovery is achieved, there are no components to loosen or
wear out and therefore you may recommence whatever activities you
wish as long as you understand that the arthritic part of the knee
can still deteriorate. The surgery works by taking the weight off
the worn out side of the knee and transferring it to the healthy side
of the knee.
« A diagram of a tibial osteotomy»
Only a small proportion of patients with knee arthritis are suitable
for this treatment. The pain relief is not as reliable as with a total
knee replacement. In appropriately selected patients there may be
a 75% chance of a good result (i.e. the pain being better than it
was before surgery) at 10 years from surgery.
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