Approximately 85% to 90% of total knee replacements are successfully maintained for more than 10 years. The main problem later on is loosening of the prosthesis, which is the result of fragmentation of the cement used to cement the bone to the prosthesis or osteolysis. Ten years after surgery, 25% of total knee replacement patients may show signs of loosening on radiographs, and 10% will be in pain and require revision surgery. Part of the loosening of the prosthesis is related to the patient’s weight and activity level, and because of this, total knee replacements are not well suited for overweight or young patients. Even if the prosthesis loosens and becomes painful, reoperation is usually, but not always, required. This is because the results of a second surgery [revision] are often less favorable than after the first surgery and complications are more likely.