The other kind are those that occur in the blood from the implant itself, which can develop several years after the implant. Fever, pain or problems moving the joint may be the only warning sign (Clin Infect Dis, November 1992). Furthermore, the constant inflammation of what is, after all, a foreign body inside a human being can set up a recipe for more serious disease. In one study, a malignancy developed at the side of the infected implants (Ortho Rev, May 1994)."I have two total knee replacements, which have become infected with staphylococcus as a result of mismanagement during a minor throat inspection," writes George, a 75 year old from Weymouth. "After a long period of treatment with flucloxacillin tablets I am told I shall have to continue with this for life." George's alternative to taking antibiotics forever is to have the joints replaced again and to face potential failure, a prospect, at his age, he is loathe to consider.

George's experience isn't as rare as it might seem. Associations have been made between oral infection and subsequent blood infection after total joint replacement operations, particularly if the patients have periodontal disease. The usual medical solution is to give joint replacement patients intravenous antibiotics as a just in case measure during the operation and use double latex gloves. If the joint does become infected, despite these precautions, the surgeon will try to give antibiotics indefinitely, or operate again if the infection is caught in two weeks, do a revision operation in two stages, or replace the joint again. However, studies have found that some of the staph germs are resistent to antibiotics (J of Bone & Joint Surg, September 1994).

When the infection can't be controlled, the only solutions are amputation, in the case of knee replacements, and fusing the bones together, in the case of hip replacements, which can leave one leg two to three inches short (Cur Op Rheuma, March 1994).