What is knee replacement?
Joint replacement involves surgery to replace the ends of bones
in a damaged joint. This surgery creates new joint surfaces.
In knee replacement surgery, the ends of the damaged thigh and
lower leg (shin) bones and usually the kneecap are capped with
artificial surfaces lined with metal and plastic. Usually, doctors
replace the entire surface at the ends of the thigh and lower
leg bones. However, it is increasingly popular to replace just
the inner knee surfaces or the outer knee surfaces, depending
on the location of damage. This is called unicompartmental replacement.
People who are good candidates for unicompartmental surgery have
better results with this procedure than with total joint replacement.1
Doctors usually secure knee joint components to the bones with
cement.
In knee replacement surgery, doctors remove the damaged cartilage
and replace it with new joint surfaces in a step-by-step process.
Causes For Knee Joint Replacement
There are many conditions that result in degeneration of the knee
joint. Osteoarthritis is the most common cause for patients who
have knee replacement surgery. Osteoarthritis is commonly referred
to as "wear and tear arthritis". Osteoarthritis can
occur with no previous injury to the knee joint - the knee simply
"wears out". Some people may have a genetic tendency
that increases their chances of developing osteoarthritis.
The major problem in osteoarthritis is that the cartilage (the
articular cartilage) on the surface of the bone inside the joint
wears away. Once the slick protective surface of the articular
cartilage is worn away, the results is bone rubbing against bone.
Bone rubbing against bone is painful.
Fractures of the knee, torn cartilage, and torn ligaments can
cause the knee joint to function abnormally. This abnormal function
can lead to excessive wear and tear of the joint many years after
the injury - just like an out-of-balance tire can wear out too
soon.
Symptoms
The symptoms of a degenerative knee joint usually begin as pain
while bearing weight on the affected knee, such as when walking.
You may start to limp. The knee may become swollen with fluid.
The range of motion of the affected knee can be affected. The
knee will bend less than normal and may lose its ability to completely
straighten out. Bone spurs will usually develop and can be seen
on xray. Finally, as the condition worsens, you may feel pain
may almost all of the time. Pain may even keep you awake at night.
Medical Treatment
Not all degenerative knee conditions require a knee replacement
as a first treatment. Your doctor may suggest several alternative
treatments to put off replacing the knee as long as possible.
Using a cane may help relieve some of your pain and allow you
to walk more comfortably. Anti-inflammatory medicines may reduce
the inflammation from the arthritis and reduce pain.
The Artificial Knee Joint, called a prosthesis
There are two main types of artificial knee replacements:
• Cemented Prosthesis
• Uncemented Prosthesis
Both types are widely used. The kneecap, or patellar, portion
of the prosthesis is usually cemented into place. The choice to
use a cemented or uncemented prosthesis is usually made by the
surgeon based on your age and lifestyle, and your surgeon's experience.
Each prosthesis has four parts:
• The tibial component replaces the end of the tibia. The
tibia is commonly called the shinbone.
• The femoral component replaces the end of the femur, the
groove where the kneecap slides. The femur is commonly called
the thighbone. It is the largest bone in the body.
• The patellar component replaces the surface on bottom
of the patella. The "top" of the kneecap is the part
you can feel through your skin. The "bottom" is the
on the other side, and slides up and down in the femoral groove
whenever you bend or straighten your leg.
The femoral component is made of metal. The tibial component is
usually made of two parts - a metal tray that is fitted directly
onto the bone, and a plastic spacer that provides a bearing surface.
The plastic used is very tough and very slick - so slick and tough
that you could ice skate on a sheet of the plastic without much
damage to the plastic.
A cemented prosthesis is held in place using an epoxy type cement
that attaches the metal to the bone. An uncemented prosthesis
has a fine mesh of holes on the surface that allows the bone to
grow into the mesh and attaches the prosthesis to the bone.
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How
to Prepare for Surgery and Recovery
People can do many things before and after they have surgery to
make everyday tasks easier and help speed their recovery.
Before Surgery
• Learn what to expect.
• Arrange for someone to help you around the house for a week
or two after coming home from the hospital.
• Arrange for transportation to and from the aeroport.
• Set up a “recovery station” at home. Place the
television remote control, radio, telephone, medicine, tissues,
wastebasket, and pitcher and glass next to the spot where you will
spend the most time while you recover.
• Place items you use every day at arm level to avoid reaching
up or bending down.
• Stock up on kitchen supplies and prepare food in advance,
such as frozen casseroles or soups that can be reheated and served
easily.
After Surgery
• Follow the doctor’s instructions.
• Work with a physical therapist or other health care professional
to rehabilitate your knee.
• Wear an apron for carrying things around the house. This
leaves hands and arms free for balance or to use crutches.
• Use a long-handled “reacher” to turn on lights
or grab things that are beyond arm’s length. Hospital personnel
may provide one of these or suggest where to buy one.
The Surgery
Most degenerative problems will eventually require replacement of
the painful knee with an artificial knee joint, called a prosthesis.
The decision to proceed with surgery should be made by you, your
family, and your doctor and only after you feel that you understand
as much as possible about the surgery and recovery process.
Hundreds of knee replacement surgeries have been
performed in Tunisia and this operation has an excellent safety
record. Some of the important steps in the operation are as follows:
 General or
regional anaesthesia is utilized.
Replacing
the knee needs two incisions, one on the side and the other on the
back of the knee.
During knee
replacement, a surgeon cuts away damaged bone and cartilage from
your thighbone, shinbone and kneecap and replaces it with prosthesis.
Before closing
the incision, the doctor bends and rotates your knee, testing and
balancing it to ensure that it functions properly.
Rehabilitation
While you are in the clinic:
• Range of Motion exercises
• Walking
• Exercises for strength and flexibility
The physical therapist will schedule your first visit soon after
surgery. Therapy will focus on the range of motion in the knee.
Gentle movement will be used to help you begin bending and straightening
of the knee. If your surgeon recommends a continuous passive motion
(CPM) machine, it will be adjusted for your knee. Next, you’ll
go over your exercise regimen. When you are stabilized, your therapist
will assist you up for a short walk using crutches or a walker.
Physicial therapy will continue once or twice a day. You will be
on your way home when you can safely:
• get into and out of bed,
• walk up to 75 feet with crutches or a walker,
• go up and down a flight of stairs, and
• get to the bathroom.
It is also important that you have good contraction of the upper
thigh muscle, called the quadriceps, and that the range of motion
of your knee is improved.
After you leave the clinic:
An every day physicial therapy treatment will be organized. The
therapist will go over your exercise program again.
As you progress:
Once you begin outpatient physical therapy, several key areas will
be addressed. .
Range of motion exercises will help you regain full bending and
straightening of your knee. Your exercise program will include strengthening,
balance, endurance, and functional activities. Your strengthening
program will focus on key muscle groups in the buttocks and hips,
thigh, and calf muscles. When you are allowed full weight bearing,
several balance exercises will be used to further stabilize your
knee. Endurance can be achieved by riding a stationary bike, swimming
laps, and using an upper body ergometer (upper cycle). Finally,
you will be taugh a special group of exercises that simulate your
day-to-day activities, like going up and down steps, squatting,
raising up on your toes, and bending down. Later, specific exercises
may be chosen to simulate the physical demands of your work or hobby.
More than 95 percent of people who have a total knee replacement
experience significant pain relief, improved mobility and a better
overall quality of life.
Risks of knee replacement
As with any surgery, knee replacement surgery carries the risk of
potentially life-threatening infection, heart attack and stroke.
Blood clots in the leg vein (thrombophlebitis) or in the lungs (pulmonary
embolism) are a major concern, so blood thinners are commonly used
to help prevent them.
Other risks include knee-joint infection, nerve damage, and the
possibility that your new knee could break or become dislocated.
Although the risks of such serious complications are rare, infection
is an ongoing concern. Even years after surgery, bacteria can travel
through your bloodstream and infect the surgical site. Notify your
doctor immediately if you notice such warning signs as a fever greater
than 100F, shaking chills, drainage from the surgical site, and
increasing redness, tenderness, swelling and pain in the knee. If
antibiotics fail to clear up the infection, you usually need one
surgery to remove the infected joint and another surgery to install
a new one. Your chances of a good-to-excellent outcome that reduces
pain and improves function decline with each additional surgery.
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