Introduction
A painful knee can severely affect your ability to lead a
full active life. Over the last twenty five years, major advancements in
artificial knee replacement have improved the outcome of the surgery greatly.
Artificial knee replacement surgery is becoming more and more common as the
population of the world begins to age.
Causes
There are many conditions that can result in degeneration
of the knee joint. Osteoarthritis is the most common cause that patients need
to undergo knee replacement surgery. This condition is commonly referred to as
"wear and tear arthritis". Osteoarthritis can occur with no previous
history of injury to the knee joint - the knee simply "wears out".
There may be a genetic tendency in some people 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. This results in bone rubbing against bone, the slick
protective surface of the articular cartilage is absent. This causes pain.
Abnormalities of knee joint function resulting from
fractures of the knee, torn cartilages and torn ligaments can lead to
degeneration many years after the injury. The mechanical abnormality leads to
excessive wear and tear - just like the out of balance tire that wears out too
soon on your car. For more information of these injuries, see
meniscus
and cartilage injuries
Symptoms
The symptoms of a degenerative knee joint usually begin as
pain while bearing weight on the affected knee. You may limp and the knee may
become swollen with fluid. The degeneration can lead to a reduction in the
range of motion of the affected knee - the knee bends less than normal and may
lose the ability to completely straighten out. Bone spurs will usually develop
and can be seen on x-ray. Finally, as the condition becomes worse, the pain
may be present all the time and may even keep you awake at night.
Diagnosis
The diagnosis of a degenerative knee starts with a complete
history and physical examination by your doctor. X-rays will be required to
determine the extent of the degenerative process and may suggest a cause for
the degeneration. Other tests may be required if there is reason to believe
that other conditions are contributing to the degenerative process. Blood
tests may be required to rule out systemic arthritis (such as Rheumatoid
Arthritis) or infection in the knee.
Medical Treatment
Not all degenerative knee conditions require a knee
replacement as the initial treatment. Your doctor may suggest several
alternative treatments to put off the decision for replacing the knee as long
as possible. Using a cane may help alleviate some of your pain and allow you
to walk more comfortably. Anti-inflammatory medications may reduce the
inflammation from the arthritis and reduce your pain.
Conservative treatments are non-surgical techniques that may prevent or delay
the need for future surgical treatment. They should be considered the first
line of defense against osteoarthritis of the knee:
Diet modification can be used to help an individual lose weight. This reduces
the wear and tear put on all joints of the body and can slow down or eliminate
the deterioration process of the cartilage. Additionally, dietary supplements
can be incorporated that are thought to help preserve healthy cartilage and
bone.
Physical therapy can also help address the osteoarthritic condition. Exercise
leads to stronger muscles and better flexibility, which creates more durable
joints. Continued physical activity is a key to preserving joints, muscle and
bone.
Medical treatment through medications can help an individual manage the onset
of osteoarthritis. Over-the-counter Non-Steroidal Anti-inflammatory
Medications (NSAIDs) such as Aleveｮ Motrinｮ and Tylenolｮ may be prescribed by
your orthopaedic specialist to reduce swelling and pain. In some cases
prescription medication, such as Voltaren or Naprosyn may be administered to
address more severe cases. Newer NSAIDs such as Vioxxｮ, Celebrexｮ and Bextraｮ
work very well and have been designed specifically for the treatment of
arthritic joints. These newer prescription NSAIDs have few side-effects,
especially stomach irritation (gastritis) or ulcer formation.
Unfortunately, health insurance companies, especially HMOs, prefer not to
spend the extra money and therefore do not approve these safer medications
most of the time. Quite often, medical treatment can be used in
combination with other conservative treatment methods. When taking
NSAIDs for long term, the risk of suffering a stomach ulcer or bleed
increases.
Injection treatments are sometimes incorporated into a treatment regimen to
reduce the symptoms of osteoarthritis of the knee and are often successful in
relieving pain and delaying the need for surgical intervention.
Injectable medications include both traditional steroids which are injected by
your doctor and newer viscous substances (viscosupplementations). Both
are equally efficacious.
Oral Joint supplements, Chondroiting and
Glucosamine Sulfate are available over the counter and provide a modest amount
of pain relief in some, but not all patients, and only after taking them for
more than 3 months. Both substances should be taken together. The
brand name CosamineDS is the most popular brand but many others are probably
as effective.
Surgery
Most degenerative problems will finally require replacement
of the painful knee with an artificial knee replacement. The decision to
proceed with surgery should be made jointly by you and your doctor only after
you feel that you understand as much about the procedure as possible.
Once the decision to proceed with surgery is made, there
are several things that may need to be done. Your orthopedic surgeon may
suggest a complete physical examination by your medical or family doctor. This
is to ensure that you are in the best possible condition to undergo the
operation. You may also need to spend time with the Physical Therapist who
will be managing your rehabilitation after the surgery. The therapist will be
able to begin the teaching process before the surgery to ensure that you are
ready for the rehabilitation afterwards.
One purpose of the preoperative visit is to record a
baseline of information. This includes your measurements of your current pain
levels, functional abilities, the presence of swelling, and the available
movement and strength of each knee.
A second purpose of the preoperative visit is to prepare
you for your upcoming surgery. You値l begin to practice some of the
exercises you値l use just after surgery. You値l also be trained in the use
of either a walker or crutches. Whether the surgeon used a cemented or
noncemented approach will determine how much weight you値l be able to apply
through your foot while walking Finally, an assessment will be made of any
needs you値l have at home once you池e released from the hospital.
Finally, you may be asked to donate some of your own
blood before the operation. This blood can be donated 3-5 weeks before the
operation and your body will make new blood cells to replace the loss. At the
time of the operation, you will receive your own blood back from the blood
bank in case you need to have a blood transfusion.
The Artificial Knee
There are two major types of artificial knee replacements:
- Cemented Prosthesis
- Uncemented Prosthesis
Both are still widely used. In many cases a combination of
the two types are used. The patellar (knee cap) portion of the prosthesis is
commonly cemented into place. The choice to use a cemented or uncemented
artificial knee is usually made by the surgeon based on your age, your
lifestyle, and the surgeons experience.
Each prosthesis is made up of four parts:
- The tibial component (bottom portion) replaces the
top of the lower bone, the tibia.
- The femoral component (top portion) replaces the two
femoral condyles and the groove where the patella runs.
- The patellar component (kneecap portion) replaces the
joint surface on the bottom of the patella that rubs against the femur in
the femoral groove.
The femoral component is made of metal. The tibial
component is usually made up of two parts - a metal tray that is
attached directly to the bone and a plastic spacer that provides the bearing
surface. The plastic used is very tough and very slick - (so slick and tough
that you can ice skate on a sheet of the plastic with out much damage to the
material).
A cemented prosthesis is held in place by a type of
epoxy cement that attaches the metal to the bone. An uncemented prosthesis has
a fine mesh of holes on the surface that allows bone to grow into the mesh and
attach the prosthesis to the bone.
Rehabilitation
While you are in the hospital:
- Range of Motion (ROM)
- Ambulation (walking)
- Exercises
The physical therapist will schedule your first inpatient
visit shortly after surgery. Treatment will address the range of motion in the
knee. Gentle movement will be used to begin to help you regain both the
bending and straightening of the knee. If you are using a CPM (continuous
passive motion) device, it will be checked for alignment and settings. Next,
you値l go over your exercise regimen. When you are stabilized, your
therapist will assist you up for a short outing using your crutches or your
walker. Treatment will proceed on a one to two time per day basis. You値l be
on your way home when you can demonstrate a safe ability to get in and out of
bed, walk up to 75 feet with your crutches or walker, get up and down flight
of stairs and access the bathroom. It is also important that you regain a good
muscle contraction of the upper thigh muscle (quadriceps) and that you gain
improved knee range of motion.
After you leave the hospital:
- Home health needs
Once discharged from the hospital, your therapist will
likely see you for in home treatment. This is to ensure you are safe in and
about the home. You should be seen for at least one visit for the safety check
and to review your exercise program. In some cases you may require up to three
visits at home before beginning outpatient physical therapy.
As you progress:
- Outpatient progression
Welcome to outpatient physical therapy. Several key areas
will be addressed. Your therapist may choose one or more modalities such as
heat, ice, or electrical stimulation to help reduce persistent swelling or
pain. Continue to use your walker or crutches. If you had a cemented
procedure, you値l advance the weight you place through your sore leg as much
as you feel comfortable. If yours was a noncemented procedure, place only the
toes down until you致e had a follow-up x-ray and your doctor or therapist
directs you to advance the amount of weight through your leg (usually by the
5th or 6th week postoperatively). Range of motion exercises and techniques
will be used to help you regain full bending and straightening of the knee. An
exercise program will be developed including strengthening, balance, and
endurance, and functional activities. Your strengthening program will address
key muscle groups including the buttock and hips, thigh, and calf muscles.
When you are safe in putting full weight through the leg, several balance
exercises can be chosen to further stabilize and control the knee. Endurance
can be achieved through stationary biking, lap swimming, and using and upper
body ergometer (upper cycle). Finally, a select group of exercises can be used
to simulate day-to-day activities, like going up and down steps, squatting,
raising up on your toes, and bending down. Specific exercises may then be
chosen to simulate work or hobby demands.
Complications
As with all major surgical procedures, complications can
occur. Some of the most common complications following knee replacement are:
Infection
Infection can be a very serious complication following
an artificial joint. The chance of getting an infection following artificial
knee replacement is probably somewhere around 1%. Some infections may show up
very early - before you leave the hospital. Others may not become apparent for
months, or even years, after the operation. Infection can spread into the
artificial joint from other infected areas. Your surgeon may want to make sure
that you take antibiotics when you have dental work, or surgical procedures on
your bladder and colon to reduce the risk of spreading germs to the joint.
Stiffness
In some cases, the ability to bend the knee does not
return to normal after an artificial knee replacement. Many orthopedic
surgeons are now using a machine known as a CPM machine (Constant Passive
Motion) immediately after surgery to try and increase the range of motion
following artificial knee replacement. Other orthopedic surgeons rely on
physical therapy beginning immediately after the surgery to regain the motion.
It is not clear which is the best approach. Both approaches have benefits and
risks, and the choice is usually made by the surgeon based on his experience
and preferences.
To be able to use the leg effectively to rise from a
chair, the knee must bend at least to 90 degrees. A desirable range of motion
should be greater than 110 degrees. Balancing of the ligaments and soft
tissues (during surgery) is the most important determining factor in regaining
an adequate range of motion following knee replacement, but sometimes
increasing scarring after surgery can lead to an increasingly stiff knee. If
this occurs, your surgeon may recommend taking you back to the operating room,
placing you under anesthesia once again, and forcefully manipulating the knee
to regain motion. Basically, this allows the surgeon to breakup and stretch
the scar tissue without you feeling it. The goal is to increase the motion in
the knee without injuring the joint.
Loosening
The major reason that artificial joints
eventually fail continues to be a process of loosening where the metal or
cement meets the bone. There have been great advances in extending how long an
artificial joint will last, but most will eventually loosen and require a
revision. Hopefully, you can expect 10-15 years of service from an artificial
knee, but in some cases the knee will loosen earlier than that. A loose
prosthesis is a problem because it causes pain. Once the pain becomes
unbearable, another operation will probably be required to revise the knee
