is a Total Knee Replacement?
knee is a complicated joint which is made up of muscle, tendons,
ligaments, and bones. These components permit it to move in a number
of directions enabling us to sit, stand, walk, climb stairs, and
change direction (pivot). There are three bones: the femur (thigh
bone), the tibia (shin bone), and the patella (knee cap). The surface
of the ends of these bones is covered in cartilage. A cartilage
pad, called the meniscus, sits between the femur and the tibia.
The entire joint is bathed in a slippery fluid - synovial fluid
- which lubricates the joint and also supplies the cartilage with
nutrients. The knee can be damaged by trauma (for example, falls,
sports injuries, car accidents) or through disease such as with
arthritis. Following trauma or disease, the articular cartilage
wears away and raw bone begins to rub against raw bone. Once enough
damage has occurred, the knee becomes painful and causes discomfort,
limping, instability, giving way, and swelling, resulting in a decrease
in the motion and function of the knee joint.
a surgical procedure which involves the replacement of the worn-out
parts of the knee with an artificial joint. A total knee replacement
implies that everything about the joint is being replaced - which
isn't true. What is actually being done is just a resurfacing of
the bones of the joint. The prosthesis that is used is made up of
plastic and metal and is placed on the joint surface of each bone.
Most of the ligaments and all of the tendons remain intact. This
allows the bones to glide against each other and allow the knee
to bend and move without pain.
is important for you to realize that this is an elective surgical
procedure which means that you have to choose it. It's not absolutely
essential, although almost certainly you would be improved by it
as long as there are no major complications. The reason for this
report is to provide you with the kind of information as well as
answers to some typical questions that will help you make that decision.
the knee is damaged to the point that it is painful or that it can
no longer move in the way that it is intended, the patient goes
to a physician to see if anything can be done to change this situation.
There are things that can be done other than knee replacement for
people who have problems with their knees. Whether those things
are likely to be successful, depends a little bit on the specific
individual circumstances. One of the alternatives to total knee
replacement, of course, is to do nothing, simply to continue with
your present disability and your present discomfort and modifying
those, if possible, with:
medications and pain killers
your activities using a cane or crutches.
may be a reasonable alternative for some people. Others, once
they learn what is required may prefer a total knee replacement.
There are also surgical procedures that are lesser surgical procedures
than total knee replacement such as: osteotomy, arthroscopic debridement,
and synovectomy. These surgical procedures should be discussed
with you to determine if they are reasonable alternatives in your
case. Depending on the stage of your disease or damage, total
joint replacement may be the only reasonable surgical procedure.
This means that basically the choice is either to proceed with
a total joint replacement or simply to wait a little bit longer
to see how rapidly your condition deteriorates and to try some
other things including medication, limitation of activity, weight
Should You Expect?
patients who have a knee replacement will require blood transfusion.
If you are donating blood for your surgery, you will be asked to
donate one or two units of your own blood within 35 days prior to
your surgery date. This will involve scheduling an appointment with
the blood bank of the hospital, or if necessary, a blood donation
facility recommended by your insurance carrier or one closer to
where you live (for out-of-state patients). Only one unit of blood
can be donated at a time, so you may need to come in for two visits.
The blood is then stored until your operation.
you are unable to donate blood, for whatever reason, donor blood
will be used in your case, if necessary. People have expressed some
concern about blood transfusion because of the risk of transmitting
diseases. Donor blood is carefully screened for communicable diseases.
With the new technology, the risk of hepatitis and HIV infection
is extremely low. To our knowledge, disease transmission through
use of donated blood has never occurred in any of our patients.
However, there is no question that your own blood is the safest.
Therefore, if you are able, we recommend that you donate blood for
your surgery. If you're coming a long way, arrangements can be made
to have you give blood locally and have it transported here for
your surgery. Please be assured that blood that you give will be
given back to you, if needed.
Within two weeks prior to your surgery, you will be asked to undergo
several laboratory tests and possibly an electrocardiogram and
chest x-ray. This is called pre-admission testing. This will help
us to tell whether there are any conditions which might increase
the risk of surgery. A physical examination, performed by your
own medical doctor or hospital staff here, is also a part of pre-admission
You will not be allowed to drink or eat anything
after midnight and on the morning of the surgery. In some cases,
you may be allowed to take a medication you normally take in the
morning with a minimal amount of water. If instructed to
do so, you will need to let the admitting nurse know that you have
you come into the hospital on the day of surgery, you may have some
additional x-rays that might not have been taken previously and
have a physical examination by your surgeon or resident. If you
have not already done so, you will be asked to sign an operative
consent form to state that you understand what is being proposed
and that you are in agreement that we may proceed with the operation.
Just prior to surgery, an intravenous line will be started and you
will be taken into the operating suite.
You will be seen by an anesthesiologist on
the morning of surgery. The anesthesiologist can answer specific
questions you might have. Most of our surgeries are performed under
spinal anesthesia. This is a very safe form of anesthesia. It is
safer than general anesthesia, which is one of the reasons why we
recommend it. Spinal anesthesia disturbs the major body functions
a lot less than general anesthesia. Unless there are some specific
reasons why a spinal anesthetic should not be used in your case,
this is our preferred method of anesthesia.
anesthesiologist will give you some medication to make you sleepy
so that you're not really aware of what's going on in the operating
room. You will not be totally asleep either. However, the area
that will be operated on will be totally numb throughout the operation
and for several hours after the surgery.
As stated before, the surgery involves the
removal of all of the damaged bone and cartilage. This is done with
saws and drills much like a carpenter uses. The next step is to
prepare the bone for the prosthesis. This involves using specialized
tools to make precise cuts and to shape the bone so that the prosthesis
will fit properly. The artificial joint is then placed into the
bone with or without bone cement. The surgery itself takes between
two to three hours, depending on the complexity of your case. It
many depend on how many previous surgeries you've had, how badly
deformed your knee is, how mobile it is, etc., as to how long it
will take. The length of time is not really very important.
knee prostheses can be attached to the bone using a material called
methylmethacrylate or, more simply, bone cement. With proper technique,
this gives an immediate fixation of the prosthesis to the bone.
Another method is called biologic fixation. This method requires
that the surface of the prosthesis next to the bone is porous. With
time, bone grows into the pores and the prosthesis becomes an integrated
part of the joint. There are advantages and disadvantages to each
type of "fixation." Furthermore, the type of fixation
recommended to you will depend on your age, weight, and activity
When your surgery is completed, you will go to the recovery room
where you will be closely monitored until the effects of the anesthesia
and intra-operative medicines are decreased and you are relatively
awake and comfortable.
When you have completed your stay in the recovery room, you will
be transferred to your hospital room in the orthopaedic nursing
unit. You will be lying on your back in a comfortable position.
If you have surgery early in the morning, you may sit up on the
edge of the bed that evening. In general, all patients are out of
bed within twenty-four hours and attending physical and occupational
therapy. The therapists will instruct you in learning how to use
crutches or a walker and being taught some of the precautions that
are necessary in the immediate post-operative period. The physical
therapist will answer any of your questions and will go over all
of the details.
It is important that you understand that there are risks associated
with any major surgical procedure and total knee replacement is
no exception. This section is not meant to alarm you but you really
do need to know these kinds of things in order to make the decision
as to whether you wish to proceed with a total knee replacement.
These risks include the risk of death. That's true of any major
surgical procedure requiring anesthesia and blood transfusion. The
risk of death in our hospital for total knee replacement is in the
order of 1 per 1,000 cases so that you can see that the risk is
very small, but it's not 0. The specific risk for you will depend
upon your general medical condition, your age, and the difficulty
of the surgical procedure, but the risk of death itself is really
precautions are taken, there are other potential risks that need
to be taken into account. These include infection, limitations in
knee motion, and loosening of the prosthesis. Although these do
not occur frequently, you should be aware that they could occur.
major potential risk is the risk of infection. Again, in this hospital,
the risk of infection is in the order of 1/2% or less. 1/2% would
be l case in 200 and, in our hospital, the risk is actually 1 case
in 400. You will be receiving an antibiotic on the morning of surgery
and this will be continued for 24-36 hours after surgery. There
are other preventive measures that will also be undertaken to reduce
the possibility of infection. In spite of these, a very small percentage
of patients will develop an infection and that generally can be
treated by antibiotics and cured. This would require longer hospitalization,
treatment with antibiotics for a longer period of time, perhaps
opening and draining of the knee and, in some instances, perhaps
even removal of the artificial components themselves in order to
cure the infection after which another knee replacement could be
implanted. There is also some risk of an infection elsewhere in
your body after the surgery settling in the knee and therefore we
strongly recommend that patients who have total joint replacement
take antibiotics whenever they have infections in another area.
Antibiotics should also be taken prior to procedures such as sigmoidoscopy,
cystoscopy and routine dental work for the first two years after
surgery. For more information regarding infections and total joints
risk of total knee replacement is that the motion of the knee may
be more limited than before the surgery. To a certain extent, how
well your prosthesis moves after it's put in will depend upon how
much your knee moved before the operation. People with very stiff
knees before the operation may not get as much motion as patients
without stiff knees. In addition, some people whose knees moved
easily before the operation may actually lose some motion after
the operation. However, the important thing to understand is that
it is motion without pain that is important. If there is a lot of
motion before the operation but it is painful and after the operation
there is some limitation of motion but it is pain-free, this is
an improvement. We would like the knee to move to about 105°.
This makes it easy for the patient to get up and down stairs and
go up and down out of a chair quite easily. This will be one of
the things that you will be required to do in the post-operative
period. Physical therapy, both in the immediate post-operative period
and after you go home, is very important. It's important to recognize
that this is not something that is just going to come your way without
any participation on your part. You will have to extend some effort
to get the best possible result. We will be asking you to move your
knee in the post-operative period. We will be asking you to work
on strengthening your muscles. If, in about 10 days, you are not
getting your knee to 90°, a right angle, we may recommend a
manipulation. A manipulation means that you would be put to sleep
and your knee would be passively, physically bent for you. This
could break down some adhesions (scar tissue) that might have formed
around your knee after the surgery.
of the things that could occur is the loosening of the prosthesis.
This loosening would not happen suddenly, but it would be a gradual
process and it would be characterized by discomfort. In most instances,
if a prosthesis becomes loose, it can be corrected but that usually
means further surgery. Now what is the nature of this risk? That
depends on several circumstances. We think in general, it's probably
a cumulative risk of about 1% per year, so that if you have your
prosthesis for 20 years, the possibility of loosening over that
20 years could be as high as 1 in 5. If you have your prosthesis
for 10 years, it could be 10%. However, improvements in the instruments,
prostheses, and the surgical techniques used today may result in
a reduction in the risk of loosening.
there is a host of other possible complications if you review series
of several thousand you will see literally dozens of possible complications
that could take place but take place with exceeding rarity. Things
such as muscle ruptures, pulling off of the tendon, injuries to
nerves and blood vessels, superficial infection and opening of the
wound, and other things of this nature may occur. They don't occur
very often, but they can occur.
can you expect to be able to do with a total knee replacement, assuming
it's successful? You can do anything that requires normal walking.
You should be able to go up and down stairs easily. You should be
get in and out of a chair.
have enough movement to be able to put on your shoes and socks.
be able to walk distances that would be limited by things other
than your knee.
may well have other conditions that limit your activity. Other joints
may be involved, so it's not possible to tell you that you would
be able to walk 2-3 hours if you would be limited by something else.
Yet, we do have patients who return to very active work and who
basically walk more than a mile a day on an average basis after
a total knee replacement. However, you should be aware that knee
replacement is not meant for sports.
main thing that we would like to achieve and the main purpose for
doing a total knee replacement is to reduce your discomfort and
we would expect that most people who have a total knee replacement
would have either no pain whatsoever, or very minimal occasional
pain which would not require any medication. Obviously, there are
lots of things that can cause discomfort around the knee that have
nothing to do with a knee replacement. We do not replace tendons,
ligaments, or muscles. All of these can possibly be the source of
discomfort. Many times this type of pain can be controlled with
anti-inflammatory medication and, if you are taking that type of
medication now, it's possible that you may still need to take that
medication after the operation.