Revision Knee Replacement: When and Why It Is Redone

A revision knee replacement is a second operation to replace or repair a knee implant that has worn out, loosened, become infected, or stiffened. It is a bigger, more complex operation than the original, because the surgeon must remove the old implant and rebuild the knee. The reassuring context first: most people never need one. Knee implants typically last 15 to 20+ years, and around 90 to 95% are still in place at 10 years¹.

I have not needed a revision myself, and I hope I never do, but it was one of the questions I most wanted answered honestly before my first operation: what happens if the new knee fails. This guide, checked by a consultant orthopaedic surgeon, sets out why a revision is done, the warning signs, and the realistic outlook. For the first-time operation, see knee replacement surgery.

What is a revision knee replacement?

A revision knee replacement removes some or all of an existing knee implant and replaces it with new components. Because the first implant is fixed to bone and surrounded by scar tissue, taking it out and rebuilding the knee is more demanding than the original operation². The surgeon may need to deal with bone that has been lost, and may use specialised implants with stems or wedges to make up for it. Sometimes only one part is revised; sometimes the whole replacement is redone.

Why a knee replacement is redone

A knee replacement is redone when something has gone wrong with the implant or the joint around it. The main reasons are:

• Wear or loosening: over many years the plastic spacer wears or the implant works loose from the bone; this is the classic late reason for revision.
• Infection: about 1 to 2 in 100 original replacements become infected, and infection is one of the most serious reasons for revision³.
• Stiffness: a knee that will not bend far enough, sometimes after a manipulation under anaesthetic has not been enough.
• Instability: a knee that feels loose or gives way.
• Fracture around the implant, or ongoing unexplained pain.

The warning signs a knee replacement is failing

The warning signs include increasing or new pain, swelling that will not settle, a feeling of looseness or instability, new stiffness or reduced movement, and clicking or grinding. Signs of infection deserve urgent attention: warmth, redness, fever, or discharge from the wound, even years after surgery. None of these means a revision is certain, but all of them should be reviewed by your surgical team, who can examine the knee, take X-rays, and run blood tests. Some stiffness and a weather-change ache are normal in any new knee; a clear change for the worse is not.

How a revision is performed

A revision is performed under general or spinal anaesthetic and usually takes longer than the first operation. The surgeon removes the existing implant, cleans out worn material and scar tissue, addresses any bone loss with grafts or specialised components, and fits new parts that are tested for stability and movement. Where infection is the cause, it is often done in two stages: the implant is removed and the infection cleared first, sometimes with a temporary spacer and a course of antibiotics, before a new implant is fitted at a second operation weeks or months later². The hospital stay may be longer than the 1 to 3 days typical of a first replacement⁴.

Recovery and outlook after revision

Recovery after a revision can be longer and a little slower than after a first replacement, and the results, while usually good, are slightly less predictable. You will still rely on walking aids in the early weeks and on physiotherapy to regain bend and strength, as with any knee replacement; full recovery can take 6 to 12 months, sometimes longer. Most people get meaningful relief, but it is honest to say a revised knee is, on average, a little less likely to feel completely normal than a well-functioning first replacement, which already only feels fully natural in roughly 4 in 5 people.

Who is more likely to need a revision?

Younger, heavier, and more active patients wear implants faster and are more likely to need a revision in their lifetime, which is why surgeons weigh the timing of a first replacement carefully in younger people; we look at this in the best age for a knee replacement. People who had a partial knee replacement also have a slightly higher chance, because arthritis can spread to the parts of the knee that were left alone, and a partial can be converted to a total. Looking after your weight and keeping active without high-impact pounding gives any implant its best chance of lasting.