Short answerIn one large trial, the two operations gave similar results at five years. Partial replacement cost less. Only one trial of this size exists, so we are not sure about every group of patients.
Not enough evidence yet
What it is
A partial knee replacement resurfaces only the damaged part of the knee, usually the inner side. A total knee replacement resurfaces the whole joint. Partial replacement suits people whose arthritis is limited to one side and whose ligaments are sound.
What the research shows
randomised 528 people with arthritis of the inner side of the knee, 264 to partial and 264 to total replacement, in 27 UK hospitals. At five years, there was no significant difference in the Oxford Knee Score, the main outcome. A curve analysis over the five years favoured partial replacement slightly, but the gap was too small to matter to patients.1,2
Further operations were similar. Revision occurred in 10 of 245 people after partial replacement and 8 of 269 after total replacement. Any further operation, including revision, was needed in 22 of 245 and 28 of 269. Some patient satisfaction measures were higher after partial replacement. Partial replacement cost the health system less. The gives the detail.1,2
The surgeons were relatively experienced with partial replacement. People in the trial were suitable for either operation, so the results may not apply to every knee.
What the Australian joint registry shows
In the Australian joint registry, which records nearly every joint replacement in the country, partial knees needed another operation more often than total knees. At 10 years about 11 in 100 partial knees had been redone, compared with about 5 in 100 total knees. At 20 years it was about 26 in 100 compared with 8 in 100 . The gap was largest in younger people. In people under 55, about 39 in 100 partial knees had been redone by 20 years.
Registry figures are not a fair comparison in the way a trial is. People who have a partial knee are often younger and more active, and a partial knee may be redone more readily because changing it to a total knee is easier than redoing a total knee. The TOPKAT trial, which compared similar people, did not find more further operations after a partial knee at five years.
Risks and effort
Both operations carry the usual risks of joint replacement, including infection, stiffness, clots and the need for further surgery.
What usually works instead
Exercise, weight loss and pain relief come before surgery for most people. See Does knee replacement work better than non-surgical care? and Total Knee Replacement.
Questions people ask
Which operation is right for me?
This depends on where your arthritis is, the state of your ligaments and your surgeon’s experience. Your surgeon can assess this.
Do partial replacements fail more often?
In this trial, further operations were not more common after partial replacement. In the Australian joint registry, which follows far more people for longer, partial knees were redone about twice as often as total knees .
Is there longer follow up?
The same trial has reported longer follow up. We will review it at the next update.
What are the disadvantages of a partial knee replacement?
In the TOPKAT trial of 528 people, further operations were not more common after a partial knee, and results at five years were similar. A partial knee only suits arthritis limited to one side of the knee with sound ligaments, and the trial surgeons were experienced with it.
What age is best for a partial knee replacement?
The trial did not test age groups. Suitability depends on where the arthritis is and the state of the ligaments, not on age alone. In the Australian joint registry, partial knees in younger people were redone more often, so age is one factor to discuss with your surgeon .
Will a partial knee last as long as a total knee?
On average, not quite. In the Australian joint registry about 1 in 9 partial knees had been redone by 10 years, compared with about 1 in 20 total knees. For someone aged 66 to 70, the registry estimates about a 29 in 100 chance of another operation at some point in life after a partial knee, compared with about 12 in 100 after a total knee .
Sources
Select a source to read what the study or guideline found, in plain words, with a link to the original.
Last reviewed 24 October 2026. Next review due October 2027.
