Revision knee replacement is the operation in which a failed or failing knee prosthesis is removed and replaced. As primary knee replacement has become more common and is performed in younger patients, the number of revisions has risen. It is complex surgery that depends on accurate diagnosis of why the first knee failed.
Aseptic loosening. Polyethylene wear particles trigger an inflammatory response that resorbs bone at the implant interface, and the components gradually loosen. Malalignment of the original implant accelerates the process.
Infection. Periprosthetic joint infection may present within weeks of the index operation or years later. It is the most serious mode of failure and dictates a completely different treatment plan.
Instability. An imbalanced knee, ligament insufficiency or polyethylene wear can leave the knee giving way, particularly on stairs and slopes.
Stiffness, extensor mechanism problems and periprosthetic fracture account for most of the remainder.
Pain that returns after a period of a comfortable, well-functioning knee; pain on starting to walk; a sense of instability or giving way; recurrent swelling or warmth; a wound that discharges; fever or rigors. Persistent pain from the day of the original surgery, without an interval of relief, has a different differential diagnosis and often points to malalignment, instability or unrecognised infection.
Serial radiographs are examined for radiolucent lines, migration and osteolysis; long-leg films assess alignment. CRP and ESR are measured, and aspiration of the joint with culture and synovial cell count is performed whenever infection is a possibility — a revision must never be undertaken until infection has been excluded. CT quantifies bone loss and rotational malalignment.
In aseptic failure the implants are removed with minimal further bone loss, defects are reconstructed with metaphyseal cones, sleeves, augments or bone graft, and revision components with stems and an appropriate degree of constraint are implanted. In infection the standard is a two-stage revision: removal of all components and cement, radical debridement, an antibiotic-loaded spacer and targeted intravenous antibiotic therapy, with reimplantation once the infection is controlled. Single-stage revision is reserved for selected cases with a known, sensitive organism.
Hospital stay and rehabilitation are longer than after a primary replacement. Weight-bearing may be protected for several weeks depending on the reconstruction, and functional recovery continues for six to twelve months. Outcomes are best when failure is identified early, before major bone loss develops. Regular follow-up of every knee replacement, even a symptom-free one, is the most effective way of achieving that.
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