The short answer is 15 to 25 years for most people. The longer answer depends on who you are, what implant you received, and what you do with it.
Knee replacement is one of the most studied surgeries in orthopaedics, and the data on implant longevity keeps getting better. A 2019 Lancet study looking at registry data from six countries found that roughly 82% of total knee replacements lasted 25 years. That's a number worth sitting with. Most people who get a knee replacement in their 60s or 70s will never need another one.
But "most people" isn't everyone. And the conversation about implant lifespan has changed over the past decade as surgeons perform more replacements on younger patients.
What the survival data actually says
Orthopaedic implant studies use a metric called "survivorship," which tracks what percentage of implants are still functioning (meaning no revision surgery) at a given time point. Here's what the numbers look like across large registries:
- At 10 years: about 95-97% of total knee replacements are still in place
- At 15 years: about 90-93%
- At 20 years: about 85-90%
- At 25 years: about 80-85%
Those numbers have improved steadily. Implants placed today use better materials and manufacturing processes than those from the 1990s. Cross-linked polyethylene liners wear down more slowly. Improved cementing techniques create stronger bonds. So the 25-year data, which reflects older implant technology, likely underestimates how long today's implants will last.
Partial knee replacements (unicompartmental) have slightly different numbers. They tend to have higher revision rates than total replacements, with about 77% surviving at 25 years. But partial replacements preserve more bone and natural knee function, so the revision surgery, when it happens, is often simpler.
Age matters more than you might think
Here's where it gets complicated. A 70-year-old who gets a knee replacement has a very different outlook than a 55-year-old. It's not just about the extra years of use. Younger patients are typically more active, put more stress on the implant, and have higher expectations for function.
The Australian Joint Replacement Registry shows that patients under 55 at the time of surgery have roughly double the revision rate compared to patients over 75. Part of that is mechanical wear from higher activity levels. Part of it is simply having more years for something to go wrong. A 55-year-old who lives to 85 needs that implant to work for 30 years.
This doesn't mean younger patients shouldn't get knee replacements. It means the decision requires a realistic conversation about the possibility of revision surgery down the road.
What wears out an implant
Knee replacement implants don't just "expire." They fail for specific, identifiable reasons:
Polyethylene wear. The plastic spacer between the metal components gradually wears down over years of use. Tiny particles break off and trigger an inflammatory response in the surrounding bone, a process called osteolysis. This loosens the implant from the bone. Modern cross-linked polyethylene has reduced this problem significantly.
Aseptic loosening. The bond between the implant and bone weakens over time. This is the most common reason for revision surgery, accounting for about 30% of revisions. It can happen from wear debris (see above) or from the cement breaking down.
Infection. Deep infection around a knee implant is uncommon (about 1-2% lifetime risk) but serious. It can happen shortly after surgery or years later, sometimes from a dental procedure or skin infection that seeds bacteria to the implant. Infections often require removing the implant entirely, treating with antibiotics for weeks, and then placing a new one.
Instability. The knee feels loose or gives way. This can come from ligament problems, component positioning issues, or wear.
Periprosthetic fracture. Breaking the bone around the implant, usually from a fall. More common in older patients with osteoporosis.
Factors you can control
Your surgeon picks the implant and places it. That part is out of your hands (choose your surgeon carefully). But several factors that affect implant longevity are within your control:
Body weight. Every pound of body weight translates to roughly four pounds of force across the knee during walking. A patient who is 30 pounds overweight is putting an extra 120 pounds of force on the implant with every step. Weight management after surgery is one of the most impactful things you can do for implant longevity.
Activity level. Walking, swimming, cycling, golf, and light hiking are all fine. Running, basketball, and high-impact sports accelerate wear. Most surgeons advise against repetitive impact activities, though some patients do return to running on a case-by-case basis. The implant doesn't care about your one weekend hike. It cares about the cumulative load over thousands of days.
Muscle strength. Strong quadriceps and hamstrings reduce stress on the implant by absorbing shock and stabilizing the joint. Continuing exercises from physical therapy long after you've been discharged makes a real difference.
Smoking. Smoking impairs blood flow to bone and slows healing. It increases infection risk both immediately after surgery and long-term. If you're getting a knee replacement, quitting smoking is one of the best things you can do for the outcome.
Recognizing implant failure
An implant doesn't fail suddenly. The signs build gradually:
- Increasing pain, especially with weight-bearing, that wasn't there a year ago
- Swelling that comes and goes without an obvious cause
- A feeling of instability or the knee shifting
- Grinding, clicking, or catching that's new
- Decreased range of motion compared to your post-recovery baseline
If you notice these symptoms ten or fifteen years after surgery, don't ignore them. Early evaluation gives your surgeon more options. An X-ray can show loosening, wear, or bone loss around the implant. Sometimes the fix is straightforward. Waiting until the bone is severely damaged makes revision surgery harder.
What revision surgery looks like
Revision knee replacement is a bigger operation than the original. The surgeon has to remove the old components, often deal with bone loss, and place larger implants with stems that anchor deeper into the bone. Recovery takes longer. The functional outcome is generally good but tends to be a step below what the original replacement achieved.
About 6% of knee replacement patients will eventually need revision surgery. For patients under 55, that number is closer to 10-15% over their lifetime.
The encouraging part: revision implant technology has also improved. And if your first replacement lasts 20 years, the revision techniques available two decades from now will likely be better than what exists today.
The bottom line for your decision
If you're researching knee replacement longevity because you're trying to decide whether to have surgery, the relevant question isn't "how long will it last" in isolation. It's "how long will it last compared to how I'm living right now."
A knee replacement that gives you 20 years of walking without pain, sleeping through the night, and keeping up with your daily life is a different calculation than an abstract number on a chart. Talk to your surgeon about your specific situation, your age, your activity goals, and your risk factors. The numbers above are averages. Your result will be yours.