Revision total knee replacement covers a very wide spectrum of topics. Exactly what is necessary at the time of revision total knee replacement is related to the very specific problem. Revisions may be as simple as exchanging a plastic bearing and leaving the components that are fixed to the bone undisturbed or may be exceedingly complex, involving major loss of bone and associated loss of mechanical integrity of the femur, tibia, quadriceps, or ligaments. Causes for revision are loosening of the components, wear of the components, ligament instability, knee cap joint instability, and infection. In general, failed total knee replacements are addressed by determining the cause of the failure and revising the knee replacement in whatever way is necessary to solve the problem.