First of all, knee replacement is something you’ll want to avoid as long as possible. You’ll want to try out all non-surgical treatments before even considering knee replacement. Maybe in the future, joint replacements will be better than anatomical joints, and people gladly will replace their healthy joints with artificial joints in order to avoid knee injuries and increase their performance. For now, however, it’s nothing more than science fiction. The good news is that modern knee replacement is normally expected to last ten to 15 years, and thanks to knee replacements, many people have been able to return to their normal day-to-day activities.
With knee replacements, damaged or worn-out surfaces of knee joints are removed and replaced by artificial surfaces. The implant or prosthesis is made of metal and plastic. Plastic used in implants is polyethylene, and the metal is titanum or cobalt-chrome.
X-ray of total knee replacement. Photo available under GNU Free Documentation License.
The artificial components normally are fixed to the bone with polymethyl-methacrylate, also known as a superglue. Sometimes, the surgeon will decide not to use superglue, or there might be a hybrid solution both with or without cement and/or screws. Also, it’s possible to cut the knee joint so the implant fits perfectly, so cement would not be needed.
Actually, there are many types of knee replacements. Most knee replacements are so-called non-constrained implants, where an artificial component is present on the knee joint but is not linked to the knee joint in order to provide stability of the knee joint. In the case of non-constrained knee replacement, a person’s own ligaments and muscles have to keep stability of the knee joint. Nevertheless, the non-constrained knee replacement is the most successful, provided, of course, that patient’s own ligaments and muscles are in good enough shape.
Semi-constrained and hinged knee replacements are not so common, but sometimes they are needed to fix badly damaged knee joints. Knee joints damaged in traffic accidents or second (revision) replacements are common cases in which semi-constrained or hinged knee replacements are used. These more complicated knee replacements might sound good, but at least for now are not expected to last as long as non-constrained knee replacements.
The type of knee replacement needed obviously depends on the condition of the damaged knee joint as well as the surgeon’s preference.
Incision scar of knee replacement. Photo available under GNU Free Documentation License.
As I said, knee replacement normally will last ten to 15 years, so it eventually will fail, but in some cases, the implant might fail even earlier. Clearly, every surgical operation contains risks such as infection , but the greatest risk related to knee replacement is the early loosening of implants, which means a second (revision) knee replacement is needed to fix the earlier knee replacement.
In conclusion, knee replacement is not an easy solution to knee problems but is a last resort. However, I have read and heard that nowadays you will have a 95 percent chance of no complications and an artifical knee replacement that will last at least ten years. Don’t take my word for it. Do choose your surgeon carefully, as the experience and skills of the performing surgeon is by far the most important factor in the success of the knee replacement.
There are concerns now that atomic particles of cobalt-chrome used also in knee implants can be absorbed by tissue or enter into the bloodstream. This can cause imflammatory reactions and even cancer. Many hip joint replacements made of cobalt–chrome had been replaced recently due to severe pain immediately after hip replacement. Hip replacement is different from knee replacement, and right now, it’s not clear whether the problems are due to bad design or bad installation. Read more here , here and here