Total knee replacement (TKR) refers to an operation where all or most of the joint surface is replaced by artificial components.
Most modern replacements are called surface replacements, because they do not use stems or extensions into the bone above or below the joint. The damaged joint surface is removed to leave a precise shape onto which the artificial components can be bonded. A special plastic (polyethylene) spacer is used to separate the metal components on either side of the joint. This creates a smooth gliding surface of metal on plastic. Because of the design of the implant, friction is reduced to a minimum and the joint glides easily.
The components can be bonded to bone either by the use of orthopaedic bone cement (Polymethylmethacrylate), or special coatings on the implants which allow bone to bond directly with the implant.