Nature, Nurture, and Your Knees: An Orthopedic Surgeon on the Real Secrets to Joint Health

1. Let's start with the basics: what actually happens inside a joint as it ages, and how much of that is truly unavoidable versus within our control?

To answer your question, let me give a little background here. If we wanted to build up a joint, we would need at least two bones joining together to secure motion of a certain body part. Unfortunately, bones are rough, and alone they would make a really bad job out of it! Therefore there must be some surface smootheners: the cartilage and the synovial fluid. Then, we would need some kind of retaining structure: the ligaments, which act directly on the bones of the joint, and muscles and tendons, which act indirectly through their activation to secure stability.

Like any mechanical device, a joint wears off over time. Initially very slowly: when we are young, our body is able – up to some extent- to repair small injuries. When aging, however, cartilage gradually loses water content and elasticity, the synovial fluid that lubricates the joint thins out, and the bone underneath it (the subchondral bone) can remodel and becomes harder and less elastic. Some of this is simply biological wear that comes with cell turnover slowing down — it's part of being human. But a huge amount of what accelerates that process — inactivity, excess weight, poor muscle support around the joint, unaddressed injuries — is very much within our control. We cannot control nature, but we may still do something for the nurture. I like to tell patients that aging is the backdrop, but lifestyle is the plot.

2. There's a common belief that arthritis is simply a matter of "bad luck" or genetics. How much truth is there to that, and what factors do we underestimate?

Genetics does play a real role — some people are simply built with cartilage or joint alignment that wears faster, and family history of arthritis is a genuine risk factor. But I think we hugely underestimate mechanical and metabolic factors: how our joints are loaded day to day, muscle strength around the joint, old untreated injuries, and even low-grade inflammation from diet or excess fat tissue. Genetics loads the gun, but daily habits often pull the trigger: again, the concept of nature and nurture is the key word here.

3. What's the biggest myth you hear from patients about aging joints that you wish you could correct?

That "if it hurts, you should rest it completely." Patients often think motion is the enemy of a painful joint, when in most cases it's the opposite — moderate, well-guided movement keeps cartilage nourished and muscles supportive. Imagine the cartilage as a sponge: it has no blood supply within it, and its food comes from the synovial fluid which soaks it when the cartilage expands after being compressed. Total rest usually makes joints stiffer and weaker, not better.

4. At what age should someone realistically start thinking about joint health, and does waiting until pain shows up mean it's already too late?

Honestly, in your 20s and 30s, though almost nobody does. Building strong muscles, maintaining healthy weight, and treating injuries properly early on pays back decades later. That said, waiting until pain shows up isn't "too late" — it just means we're managing existing damage rather than preventing it. There's always something meaningful we can do, at any age.

5. Weight, movement, diet, injury history: which of these actually has the biggest influence on how our joints age, and does the answer surprise most people?

Weight tends to surprise people the most. Every extra pound puts multiple pounds of extra force through the knees with each step, so even modest weight loss can meaningfully reduce joint stress. Usually we consider a multiplier of 3 to 5. You loose 5 kg, this will reflect in less load on your knees in the range of 15 to 25 kg. Imagine what would happen if someone who is 20 or 25 kg overweight could loose that extra mass: 60 to 125 kg less bothering their poor knees!

But it's not a solo factor: we say that arthritis is a multifactorial condition. It means that it has many causes, as for example movement (or lack of it) determines muscle support, diet and excessive adipose tissue influence systemic inflammation, and history of injury can set the stage for early arthritis in a specific joint.

6. With drugs like Ozempic and Mounjaro becoming so popular for weight loss, is there truth to the idea that rapid weight loss actually benefits joint and bone health, or can it come with hidden risks like muscle and bone density loss?

There's real truth to the benefit side — significant weight loss reduces mechanical load on weight-bearing joints like knees and hips, and many patients report real symptom improvement. But there's a hidden risk: rapid weight loss, especially without resistance training, can come with substantial loss of lean muscle mass and bone density, not just fat. That's a real concern, particularly for older patients. My advice is that these medications can be part of a joint-health strategy, but they should be paired with strength training and adequate protein intake to protect muscle and bone while the weight comes off.

7. For someone who already has some joint pain or stiffness, what's the difference between what will help and what might actually make things worse?

Helpful: gentle, consistent movement, strengthening the muscles around the joint with body weight exercises such as calisthenics, low-impact cardio, and addressing weight and inflammation. What often makes things worse: complete inactivity, or swinging to the other extreme — pushing through sharp pain with high-impact activity without proper conditioning. The key difference is usually intensity and consistency — steady, moderate loading helps; sudden, excessive, or completely avoided loading tends to hurt.

8. You've treated professional athletes as well as everyday patients. Does a lifetime of high-impact sport accelerate joint degeneration, or can it also build resilience?

Both, honestly, depending on how it's done. Repetitive high-impact loading without proper recovery, technique, or strength support can accelerate wear, especially after injuries. But well-conditioned athletes often have denser bones, stronger stabilizing muscles, and better joint mechanics than sedentary people of the same age — that resilience can be protective. It is worth mentioning though that when we consider athletes, we are talking about perfectly trained bodies -and minds- who have been doing that particular activity since they were really very young. They did not have to rush their steps, they (initially) did not have to impress anyone. Someone who picks an activity which is completely new to them in adult age usually has little time do dedicate to physical activity, and they want to see results. Early. These are the ones who certainly have more risk of injuries if they don’t respects their body physiology, including the recovery time.

Another subset of patients who can easily injure themselves are those who develop, again in adult age, a huge muscle mass. As adults, our tendons cannot be strengthened as quickly as our muscles, and many times there is a mismatch between the strength and size of the muscles compared to tendons. The net result is what we commonly see, especially in gyms: severe injuries such as rupture of the biceps tendon in the elbow, the pectoralis tendon in the shoulder, the quadriceps or the patellar tendons in the knee, and the Achilles tendon in the foot. These are conditions which more often than not require immediate surgical treatment!

More generally speaking, though, the athletes I see with problems are usually the ones who played through injuries or skipped strength and recovery work, not the ones who trained smart.

9. If someone wants their joints to hold up well into their 70s and 80s, what would you tell them to start doing today?

Move regularly, prioritize strength training (especially for the muscles around your hips, knees, and core), maintain a healthy weight, and don't ignore injuries — get them properly treated or rehabbed rather than just letting pain fade. If I had to boil it down to one habit: build and preserve muscle. Strong muscles are the best shock absorbers your joints will ever have.