Total joint fixation
 There are two methods of securing the
prosthesis to the bones. One relies on an in-growth of the patient's bone
to anchor the device, and the other uses "cement". The cement is
plastic polymer that serves as an adhesive. The method of fixation
utilized is usually based on the patient's age and the quality and
condition of the patient's bone. The design of the prosthesis also
influences the method of attachment to the bone.
Total knee
function
Replacement joints come in many different sizes, and are precision
engineered to feel and move as much like a real joint as possible. Most
people with an artificial knee joint are not aware of a difference between
the feel of the implant and their original knee. The knee replacement
allows for less bending than a normal knee. In the knee suitable for
replacement, however, the range of motion is often improved
postoperatively.
Design changes continue in existing
prostheses in an effort to yield better function and longevity. A well
implanted prosthesis, in a compliant patient, usually lasts for many
years. Since many prostheses now used are improved designs, we can only
guess at their longevity. Trauma, wear or loosening may make it necessary
to replace a prosthesis. Revision replacements may have a shorter life
expectancy than primary implants. Every effort must be made to prolong the
life of the total knee which is implanted first. A maximum working life of
10-15 years is reasonable, and more is possible. The physical activity
level and patient age are strongly related to the longevity of knee
replacements.
The main object of
a total knee replacement is relief of pain. Other goals include the
correction of deformity and restoration of stability. Prosthetic design
constraints limit the range of motion to approximately 0-120. It should
be emphasized that total knee replacements are not done to allow patients
to return to unlimited activities. Fitness may be maintained by swimming,
bicycling, and walking. Golfing and even skiing in some individuals may be
considered, but impact loading such as running or jumping should be
minimized.
Candidates
for total knee replacement 
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