How long can you delay a knee replacement?

A few years ago, Northwestern University in Illinois published an interesting piece of research. It was about the “timeliness” of knee replacement surgery – the first study of its kind – and it made some surprising claims.

After following 8,000 patients who had, or were at risk of, osteoarthritis, the researchers concluded that most people weren’t having the operation when they needed it. “Ninety percent of patients with knee osteoarthritis who would potentially benefit from knee replacement are waiting too long to have it and getting less benefit,” they wrote.

On the flipside, however, the researchers also found some people were having it too early. “About 25% of patients who don’t need it are having it prematurely when the benefit is minimal,” they added.

Too long? Too early? What do these things actually mean? More on that below! But in broad terms, these findings don’t sound too farfetched to us. It’s natural to be cautious about having a major operation: most people feel like that. But on the other hand, it’s possible to be overcautious too. Or, in rarer cases, not quite cautious enough.

So what’s the right answer here – and why should you delay a knee replacement anyway?

When is the right time to have a knee replacement?

The simple answer is that, for most people, knee replacement is only recommended if you have advanced, “end-stage” osteoarthritis which is seriously impacting your everyday life. By disruption, we mean symptoms that are making life a misery: things like recurrent swelling, inflammation, stiffness, instability, and functional problems (it’s stopping you from doing basic activities). And of course pain. People with bone-on-bone arthritis often liken the pain to toothache – a gnawing background ache that can become acute, and impossible to ignore. Here’s Ed, one of our knee replacement patients: “I had tried to stay positive. I’d tried ignoring the pain. But it was becoming more frequent. I was even struggling to get to sleep at night because of it.” (You can read more about Ed’s story in this case study.)

When is it “too early” to have a knee replacement?

Most knee replacement patients are in their 70s or older. The average age is about 74. Although younger patients have replacements too (Ed was 56 when he had his), it’s rarer. Why? One reason is longevity. An artificial knee can last a long time – about 15-20 years on average, and potentially much longer. But, at some point, the implant may start to wear out – especially if you’re very active, which younger people tend to be. At that point, you would need revision surgery to replace the old joint with a new one. Revision surgery, though, is more complex, takes longer to recover from, and comes with other potential complications. Another problem with acting too soon is unpredictability. Surgeons have found patients’ outcomes tend to be less certain, and more complicated, when their arthritis was only moderate, rather than severe. These are two key reasons why doctors will ask you to hold back from a replacement operation until you really need it.

What are the risks in waiting “too long” for a knee replacement?

This is the other end of the spectrum – and, if the study is correct, the most common situation. There are several problems with putting off your knee replacement for too long:

Worsening symptoms – the stiffness, pain and functional issues will likely only get worse as you put more wear on your knee over time
Impact on daily life – as the knee deteriorates, it will become harder to stay mobile and active, preventing you from doing some of the things you most enjoy
Impact on health – taking less exercise leads to weakening of the muscles and ligaments that support and stabilise your knee; it also raises the risk of developing other health complications, or of gaining too much weight, which could stop you from being able to have the knee replacement operation
Age factor – as we get older, it takes longer for the body to recover, and the risks of having an operation begin to rise

How can I make the best decision for my knee?

Looking at both ends of the spectrum – too early and too long – you can see there’s an optimal time to have a knee replacement: a kind of “goldilocks” window when the benefits of life after surgery outweigh the negatives, hopefully setting you up for decades of pain-free activity to come. Judging when you’ve reached that window is a balance. The right answer will involve several different factors, from your age, lifestyle and activity levels to the amount of pain, functional issues and disruption you face. You may be feeling reluctant about taking the plunge – or eager to get on with it. A good orthopaedic surgeon would never try to force you into a decision either way. But they can advise, reassure and help you weigh up the pros and cons of knee replacement – and when it might make sense to go ahead.