Injuries and arthritis can cause severe damage to the ligaments that hold the knee joint
in place and facilitate its normal, pain-free function. More than a half million people
have total surgery knee replacement each year, and the accumulated experience of both
surgeons and prosthesis manufacturers has led to very good long term results in most
When knee replacement surgery is performed, the new prosthesis replaces some of the
ligaments and part of the bone. Two methods are used to hold the new prothesis in place.
Either a fast-working cement such as polymethylmethacrylate is used, or the natural bone
is allowed to grow into the surface of the knee replacement implant.
Using cement is reliable and a prosthesis implanted with cement can last more than 20
years, depending on a person’s weight and activity level. The primary cause of the
eventual failure of a cemented prosthesis is the stress to the joint caused by too much
weight or uneven weight. Uneven wear of the non-metalic portion of the artificial knee
can cause inflammation which can lead to further stress and wear.
Cementless implants were developed in the hope that natural bone growth into the textured or coated surface of the prosthesis would lead to better or longer function. This requires a longer knee replacement surgery recovery time, and there has not yet been enough medical
experience with cementless implants to conclude whether or not they have a longer useful
life than the more traditional types.
An alternative to traditional full knee replacement , for some people with degenerative
disease of the knee, is nonsurgical treatment such as with steroid injections,
arthroscopic surgery, partial knee replacement, and minimally invasive full knee
replacement. Minimally invasive knee replacement is similar to traditional surgery except
that it is performed through a smaller incision, a 4- to 6-inche incision versus an 8- to
10-inch incision. Other elements considered in minimally invasive surgery are reducing
damage to the quadirceps tendon and muscle at the front of the thigh, and mehtods to
minimize damage to other muscles.
In addition to the specific type of surgery to be performed, a person considering knee
replacement may have a choice of the type of replacement parts that are used. Some new
artificial knee parts allow much greater flexibility than older materials. Some knee
prostheses are made of ceramic and others are made of zirconium, a newer material with
the potential to last longer than older components.
This is a field in which a lot of research is underway, so as with most serious medical
questions, it is wise to obtain more than a single opinion about what choice is best.