Infection in a joint can be very serious business. If it travels via the blood supply, it can cause many other problems, even death. Joint infection can be resistant to treatment. Sometimes an antibiotic isn't enough and further surgery is needed.
There are many factors to be considered in each case. First, the general health and immune status of the patient is very important. Someone with good health and a strong immune system who doesn't have other diseases or conditions has a better chance of recovery.
The type of infection is also an important factor. Some bacteria such as Methicillin Resistant Staphylococcus aureus (MRSA) have become resistant to most antibiotics. The longer the infection is present, the worse the prognosis.
Infection can cause loosening of the implant. This can put the stability and success of the implant at risk. The surgeon will do everything possible to save the implant. But if there are too many risk factors, then it may be necessary to remove the implant and revise the knee replacement.