End-stage knee arthritis requires surgical treatment with a knee replacement. The knee joint surfaces are removed and replaced with a metal bearing surface over the distal femur (thighbone) and a metal baseplate, supporting a polyethelene (hard plastic) bearing surface. The kneecap is re-aligned as required, but is not routinely re-surfaced. Knee repacement operations are complex and require accurate ligament balancing and implant size selection. A knee that is too loose, too tight or unstable will require a revision procedure in the short term. Outcomes and survivorship of correctly placed implants are excellent with a return to normal function at around 3 months post surgery.