A common misconception is that knee replacements have a finite lifespan of 10 – 15 years, at which point they will all fail and require revision surgery. Failure in this timeframe is actually an uncommon scenario and most knee replacements are still working perfectly at this time point.
The Australian Joint Registry publishes data on the failure rates of knee replacement. In the 2017 Annual Report, the success rate after 16 years of follow up is 92%, meaning that 8 percent of patients have undergone revision surgery at this time point. Younger patients do have higher rates of revision than older patients. At 16 years follow up success rates by age group are
- < 55 – 83%
- 55 – 64 – 89%
- 65 – 74 – 93%
- > 75 – 96%
Another point to consider is the linear rate of failure. There rate of failure is not increasingly drastically at this time point. If this trend continues in the future it would imply a worst-case success rate of around 70% at 30 years follow up (in the under 55 age group).
Finally knee replacement design and material manufacture has evolved in the past 10 years, in particular making the polyethylene liner (ultra-tough plastic) more durable by cross linking and antioxidant Vitamin E treatment. This may lead to an improvement in the above results.
In summary most total knees do not fail and it is a reasonable expectation that most patients should enjoy 20 – 30 years of trouble-free usage.