A major long-term problem is loosening of the implant. This occurs either because the cement loses its hold on the implant or because the bone dissolves from around the cement. Another problem is the wearing out of the plastic insert. This causes the metal to rub against metal, resulting in poor knee function.
A repeat surgery may be needed for these problems, especially if they are painful. Usually, 1 out of 100 patients require a repeat surgery during the first year. At 10 years, the chance of needing a repeat surgery is about 10 percent, or 10 in 100 patients.
Loosening of the implant is in part related to how heavy and active you are. Your artificial knee is not designed to handle more physical stress than normal walking.
Loose, painful artificial knees can usually, but not always, be replaced. The results of a second operation are rarely as good as the first, and the risk of complications is higher. Therefore, it is important that you attend follow-up visits with your doctor as scheduled even if you are not having pain. X-rays may show the implant loosening before you develop problems.