A large registry study suggests around 8 in 10 total knee replacements are still working 25 years on — useful context when you are weighing up surgery.
One of the most common questions before knee replacement surgery is simply: how long will it last? It is a fair question — a replacement is a big decision, and no one wants to be told they will need it done again in a few years. This study set out to answer it using the best available evidence.
What the study looked at
Rather than relying on any single hospital’s results, the researchers pooled all the long-term evidence they could find — published studies and, importantly, national joint-replacement registries — that had followed patients for more than 15 years. Registries are powerful because they record almost every operation in a country, not just the ones that went well. The team looked separately at total knee replacement (the whole joint surface) and partial knee replacement (just one side of the knee). “Lasting” was defined as the implant not needing further (revision) surgery.
What they found
Drawing on national registry data covering roughly 300,000 total knee replacements, the study estimated that:
About 82% of total knee replacements were still in place at 25 years.
About 70% of partial knee replacements lasted 25 years.
The registry figures were more conservative than results reported by individual surgeons, which tended to look more optimistic — one reason large registries are so valuable.
What it means for you
For most people, a knee replacement is a genuinely long-lasting operation. On this evidence, roughly eight in ten total knee replacements are still working a quarter of a century later. That can help set realistic expectations when you are deciding whether, and when, to have surgery. It does not tell you what will happen in your case specifically — that depends on things like your age, weight, activity level and general health, which this study did not break down — but it is reassuring background for the conversation with your surgeon.
A caveat worth knowing
The very longest-term figures came from a small number of registries (chiefly Australia and Finland) and reflect implants and techniques from some years ago, so they may not perfectly predict the newest devices. The results were also not adjusted for individual factors such as age. As always, general findings like these are a starting point for a discussion, not a substitute for advice about your own knee.
Assessing this studyA standardised appraisal for clinicians and registrars — study design, strength and validity.+
Study design
Systematic review and meta-analysis of national joint-registry reports and case series (implant survival — a prognostic question).
Level of evidence
OCEBM Level 2 (prognosis) — a systematic review of large observational cohort/registry data; not randomised.
Are the results valid?
A pre-specified protocol and broad search were used, and analysis was weighted toward national registries, which capture nearly all procedures and so avoid the selection bias of single-surgeon case series. The underlying data remain observational, and long-term (25-year) estimates rest on relatively few registries (chiefly Australia and Finland).
What are the results?
Pooled 25-year implant survival was 82.3% for total knee replacement (95% CI 81.3–83.2) and 69.8% for unicompartmental replacement (95% CI 67.6–72.1). Narrow confidence intervals reflect the very large registry denominators (~300,000 total knee replacements).
Do they apply to our patients?
Highly applicable to counselling Australian patients on implant longevity — AOANJRR data feature prominently. Survival is not stratified by age, sex, BMI or implant, and older devices dominate the long-term data, so it informs expectations rather than individual prediction.
Bottom line
Strong evidence that most total knee replacements last well beyond 20 years; a defensible figure to quote when setting patient expectations, with the caveat that it is observational and unadjusted for individual risk factors.
Framework: study design graded with the Oxford Centre for Evidence-Based Medicine (OCEBM) Levels of Evidence; validity and applicability appraised in the CASP tradition.
This is a plain-language summary of published research, provided for general education. It is not medical advice and does not describe Dr Broadhead's own results. Whether any finding applies to you depends on your individual circumstances — please discuss your care with your treating team.