One of the most important concerns that candidates have for knee and hip replacement is how long this joint lasts.today, the length of the joint is calculated in such a way that if a hundred people receive that joint or that prosthesis, how many people will have it after ten years, and how many people will have it after twenty years.In the case of most prostheses that we use today, both in the knee and in the pelvis. The ten-year lifespan is above ninety-five percent and the twenty-year lifespan is above ninety percent. That is, people who undergo joint replacement surgery can be sure that the prosthesis will continue to work for them ninety percent after twenty years.