Knee replacement is now a common procedure. It is used for arthritic
knees when the patient gets too disabled by his symptoms (pain ++,
deformity, loss of function) despite a good medical treatment. By
resurfacing the damaged and worn surfaces of the knee can relieve
pain, correct leg deformity and help resume normal activities. The
longevity of the prosthesis is the main problem because it is difficult
There are different types of prosthesis (unicompartimental or total)
but the overall design is similar : the damaged surface in the shinbone
(tibia) is replaced by a metal plate and a carved sleeve of metal
is placed over the lower end of the thigh bone (femur). The metal
used is made of cobalt chrome alloy. These pieces of metal are fixed
into position using a cement or, in some cases, pressed into position
and the fixation occurs using a biological method. Between these
two metal pieces, a high density polyethylene platform is inserted.
I use a mobile-bearing prosthesis .
- In a mobile-bearing prosthesis, the femoral component and tibial
tray move across a polyethylene insert to create a dual-surface
articulation.. This helps reduce the amount of wear to the bearing
and helps prevent loosening in places where the prosthesis attaches
to bone. Mobile-bearing knees are also designed to allow greater
rotation of the knee.
- Advantages : it can reduce early wear failure. The insert's
mobility ensures congruent contact between the femoral and tibial
components and conformity or the surfaces that move together when
you bend and rotate your knee during activity.
- Disadvantages : they are less forgiving of imbalance in soft
tissues (medial and lateral collateral ligaments). They may increase
the chance of dislocation.
The kneecap : the worn out cartilage is removed along with a sliver
of the underlying bone and is replaced by a cemented plastic button.
The kneecap is said to have been resurfaced.
For my part, I always use ciment in unicompartimental replacement.
In total replacement, I use an hybrid fixation with ciment for the
tibia and the patella. The femur piece is "pressfit" without
Computer assistance is useful, particularly for difficult knees
but it does not replace the experience of the surgeon!. I use it
most of the time. For more details, you can have a look to my french
Successful results occur when patients are willing to endure quite
a bit of uncomfortable stretching and exercise early in their recovery
with the help of a physiotherapist. It requires a lot of determination
to keep stretching a painful swollen recently operated knee but
the effort is worthwhile.
Dental evaluation : although the incidence of infection after knee
replacement is very low, an infection can occur if bacteria enter
your bloodstream. Treatment of significant dental diseases (including
tooth extractions and peridontal work) should be considered before
your total knee replacement.
Urinary evaluation : a pre-operative urological evaluation is necessary
for the same reasons (urinary infection or prostate disease).
You will be admitted to the hospital on the day before surgery.If
needed, you will be evaluated by a member of the anesthesia team.
You will be moved to the recovery room, where you will remain a
few hours while your recovery from anesthesia is monitored.Your
blood pressure, and heart rate will be monitored by a nurse, who,
with the assistance of the doctor, will determine when you are ready
to leave the recovery room. Then you will be taken either to your
hospital room or to special room for 24 hours to continue monitoring
Medication will be given to you to make you feel as comfortable
as possible.Pain management is very important for you and for us.
You will have blood thinners to prevent blood clots.
Foot and ankle movement is encouraged immediately following surgery
to increase blood flow in your leg muscles to help prevent leg swelling
and blood clots. Most patients begin exercising their knee by tightening
their thigh muscle immediately following surgery.
After 24 hours rest, the patient is able to get out of bed. He
is helped walking as soon as the second day, either using a frame
or crutches. He starts to bend his knee with the physiotherapist
and with the help of a continuous passive motion (CPM) machine.
This machine gently and steadily bends and straightens the knee.
Over the following week, the patient increase his knee flexion and
the amount he is able to walk on sticks. He will then try to walk
up and down the stairs.
The inpatient stay is usually between 8 and 12 days. Physiotherapy
is continued as an outpatient for a varying amount of time up to
two months. To check on progress, I will see you again six weeks
later or at anytime if necessary. You must keep me informed as you
go along of every problem you may have: this is important to allow
rapid diagnose and treatment of possible complications +++.
After surgery, you may either go back home (you will need help
for several weeks with such tasks as cooking, shopping, bathing,
and doing laundry) or go for a short stay in an extended-care facility
during your recovery before going home.
Wound care : Staples running along your wound will be removed two
to three weeks after surgery.Avoid soaking the wound in water until
the wound has thoroughly sealed and dried.
Some loss of appetite is common for several weeks after surgery.
A balanced diet is important to promote proper tissue healing and
to restore muscle strength
After you return home
The exercises recommended are a crucial part of your recovery,
so it is essential to continue to do them. An average of 115°
of motion is generally anticipated after surgery. Your activity
program should include
- a graduated walking program to slowly increase your mobility
in your home and later outside.
- Resuming other normal household activities, such as sitting
and standing and climbing stairs
- Specific exercises several times a day to restore movement and
strengthen your knee. You will do them by yourself and with a
physical therapist who will come home three to five times a week.
- When you are resting, you should rest with your leg raised to
help prevent swelling of the leg and ankle.
Driving : You should not drive until you are confident that you
could perform an emergency stop without discomfort.Most individuals
resume driving approximately 4 to 8 weeks after surgery;
Depending on the type of work you do, you can usually return to
work after two or three months.
Avoiding problems after surgery :
- Avoid falls and injuries
- For the first 2 years after your knee replacement, you must
take preventive antibiotics before dental or surgical procedures
that could allow bacteria to enter your bloodstream.
- After 2 years, talk to your orthopaedist and your dentist or
urologist to see if you still need preventive antibiotics before
any scheduled procedures.
- See your orthopaedic surgeon once a year,for a routine follow-up
examination and x-rays.
A knee replacement is a commonly performed and generally safe surgical
procedure. For most people, the benefits are far greater than the
However, in order to make an informed decision and give your consent,
you need to be aware of the possible side-effects and the risk of
Side effects : after surgery your knee will be sore when you move
it and swollen for up to three months. You will have a scar in front
of the knee. The scar and the outer side of the knee may be numb,
which can sometimes be permanent.
Complications are when problems occur during or after the procedure.
Most people are not affected. The main complications of any operation
are bleeding during or soon after the procedure, infection and an
abnormal reaction to the anaesthetic.
Some complications specific to a knee replacement :
- A blood clot can develop in the veins of the leg (deep vein
thrombosis, DVP). This clot can break off and cause a blockage
in the lungs. It is usually treatable, but it can be a life-threatening
- The wound or the joint can get infected. Antibiotics are given
during surgery to help prevent this.
- Sometimes it is not possible to make the new knee fully stable
and you may need to have another operation.
- A build-up scar tissue occasionnally restricts movement. Another
operation may be performed to break down the scar tissue. In rare
cases, the loss of movement may be permanent.
- The knee cap can become dislocated after surgery.
Docteur Jean Etienne Perraudin,
last updated 1 Sept 2012