Here is a question I ask patients more often than they expect: not how old are you?, but how old are your knees?
They are rarely the same number.
I'm Dr Arj Imbuldeniya, a Consultant Orthopaedic Knee & Hip Surgeon, and I've spent more than 25 years assessing, treating and operating on knees. The single most important thing I've learned is this: a knee starts ageing long before it starts hurting. By the time pain arrives, a lot has often already happened quietly underneath. The good news — and it is genuinely good news — is that much of it is modifiable, if you know where you stand.
That's what “Knee Age” is for.
Your chronological age and your knee age are not the same thing
Two people can be 50 years old and have knees that behave like they're decades apart.
One has kept their leg muscles strong, their weight stable, their metabolic health in reasonable order, and has stayed active without grinding their joints into the ground. The other has lost muscle, gained inflammatory load, slept badly for years and moved very little. On paper, same age. Biologically, their knees are living in different decades.
“Knee Age” is simply a way of describing how old your knees are biologically — how well they're actually functioning and how fast they're likely to be ageing — rather than how many birthdays you've had. It turns something invisible into a single, honest number you can act on.
Why joints age before they hurt
This is the part most people are never told.
The processes that age a knee — gradual cartilage change, loss of the muscle that protects and controls the joint, low-grade metabolic inflammation — typically begin in the 30s and 40s. They are slow, silent and painless at first. Pain is usually a late signal, not an early one.
By the time a knee genuinely hurts, the easiest window for prevention has often already narrowed. That doesn't mean it's too late — far from it — but it does mean that waiting for pain before paying attention is, biologically, waiting quite a long time.
This is exactly why I built OrthoLongevity around a simple idea: biology-first, surgery-last. I operate every week, and a well-timed, well-chosen operation can be transformative — surgery-last has never meant surgery-never. It means we reach an operation, when one is genuinely needed, with the muscles as strong as possible and the biology as good as we can get it, so the result is better. In my own practice between 2016 and 2026, around 90% of patients who came to me thinking they needed surgery didn't end up needing it — not because an operation was withheld, but because the biology was addressed in time. But for most knees, the more valuable conversation happens years earlier, before anyone's anywhere near a theatre.
A scan shows structure. It doesn't show the whole knee
People often assume an MRI or X-ray tells you everything about a joint. It doesn't.
A scan is very good at showing structure — the state of the cartilage, the bone, a meniscus. What it cannot show you is how strong the surrounding muscle is, how your metabolism is influencing inflammation inside the joint, what your genetic risk looks like, or how well your body recovers from load. Those things matter enormously for how a knee ages — and no single test, and often no single specialist, captures all of them at once.
That fragmentation is one of the real problems in joint care today. A scan here, a physio assessment there, a blood test somewhere else — and nobody pulling the whole picture together. It's how knee care fails in two opposite directions: some people end up having an operation they could have avoided, while others are quietly steered away from one they genuinely needed. Both come from the wrong person at the wrong time, with no one accountable for the whole journey.
The five things that actually determine how your knees age
When I assess a knee properly, I'm looking across five connected drivers:
- Structure — the cartilage, bone and meniscus (what a scan shows).
- Strength and capacity — the muscle that protects and controls the joint. Often the most underrated and the most fixable.
- Metabolic health — weight, inflammation, blood-sugar control. Your joints sit inside your overall biology, not apart from it.
- Genetic risk — some of us are simply dealt a faster-ageing hand. Worth knowing, not worth fearing.
- Recovery function — sleep, stress and how well your body repairs after load.
A knee that's strong, well-recovered and metabolically healthy ages very differently from one that isn't — even with identical scans. Your Knee Age is an attempt to weigh all five into one usable number, rather than leaving them scattered.
What your Knee Age can — and can't — tell you
The Knee Age test is an assessment, not a diagnosis. It gives you an evidence-informed estimate of how your knees are tracking and which drivers deserve your attention — a way to find out where you actually stand and what to focus on first. It is not a substitute for proper clinical evaluation. If you have persistent or severe symptoms — a knee that locks, gives way, swells significantly, or pain that follows an injury — that needs a proper in-person assessment, not a quiz. The two work together: the test tells you whether and where to look more closely.
How to find your Knee Age
The reason I helped create the Knee Age test is simple: the kind of complete, coordinated picture of joint health that used to be reserved for elite athletes should be available to everyone — and the first step should be free and take less time than making a coffee.
So that's what it is. The Knee Age test is a 60-second, surgeon-designed self-assessment. No account, no cost. You answer a short set of questions and get a single number — your Knee Age — along with a sense of which of the five drivers matters most for you right now.
If you take one thing from this article, let it be this: don't wait for pain to tell you how your knees are doing. Find out now, while the most is still modifiable.