Norman Swan (2:43)

I know I have heard that story before, but still, listening to you talking about your knee cap jumping out of its socket really actually made me ret.

Mark Humphries (2:51)

I'm sorry, I did put a warning there.

Norman Swan (2:53)

But you did, you did.

Mark Humphries (2:54)

You didn't have to actually cover the kitty's ears for anything. But that's what we're going to be talking about today is running and your knee. Is it bad for it or not?

Norman Swan (3:06)

That's right, because you're listening to what's that Rash? The show where we answer the health questions that everyone is asking.

Mark Humphries (3:14)

And our question today comes from Ben.

Norman Swan (3:16)

Ben says, I've been a regular listener to your podcast since the good old coronacast days. You represent Ben and look forward to hearing from you each week. Ben says, I enjoy the information that you share and the banter between the two of you. But Ben has a question he's been meaning to ask for quite a while and has finally got around to it. As I sit down, Ben says, for a big bowl of pasta after a 20 kilometre run. Way to flex. Ben says, I'm a regular runner in my mid-40s and I wonder whether this is doing good or harm to my hip and knee joints. This feels particularly relevant to me because my father and paternal grandfather have both undergone multiple hip replacements and both my parents have had knee replacements. Ben continues, while doing my own research, I seem to be able to find plenty of arguments for both sides. Some saying it's wearing down the joints, others. Others saying the regular stress or impacts keeps the joints strong. Therefore, I would love to get your diligently researched and educated feedback on the topic. Norman, I don't know anyone who's more diligently researched and educated themselves on this than you.

Mark Humphries (4:17)

I have skin in this game, Ben, so welcome to it. Yeah, and we've broadcast a lot of it in our sister podcast, the Health Report. So this is common belief. I interviewed an orthopaedic surgeon many years ago from Adelaide. I think it was from Adelaide. Anyway, asking about why we in Australia had some of the highest knee replacement rates in the world and he put it down to running and exercise and we're just grinding our knee joints to sand.

Norman Swan (4:43)

Are we really running more than other countries?

Mark Humphries (4:45)

Well, Adelaide is, I mean, South Australia is like the world capital has been in the past, anyway, world capital for knee replacements and knee interventions. And you'd have to say, I'm not sure the South Australians are any more, you know, they're fabulous people, but I'm not sure they're running any more than any other Australians. And there is a bit of mythology in this. We've also had Professor David Hunter on, who is a rheumatologist at the University of Sydney and is one of the few people in the world who actually studies osteoarthritis. Most rheumatologists study the rare, rare autoimmune diseases, and he reckons a lot of this is actually mythology.

Norman Swan (5:20)

I want to take a step back. You said South Australia has one of the highest rates of knee replacements in the world. Is that more to do with the knees or the doctors holding the scalpels?

Mark Humphries (5:29)

I think if you talk to private health insurers, they would say it's a lot to do with the doctors. It's also a lot to do with general practitioners and patients insisting, I've got a pain in the knee, I want an MRI scan. And the MRI scan shows devastation in the knee, and people get scared. And they're heading towards knee replacements, and they've been told what a marvelous operation a knee replacement is, and they head down for knee replacements. And when you really need a knee replacement, it is a marvellous operation, but you can actually fix up knee pain quite significantly, and running might be one way to do it.

Norman Swan (6:02)

Okay, so you talked about mythology. There's so much I want to dig into here, but I feel like it would be useful for us to start with a bit of the physiology of what's happening in our bodies when we run, the kind of mechanics of running.

Mark Humphries (6:15)

Well, let's talk about the metabolism of running. So running jogging is thought to be one of the best exercises you can do because it is more than just moderate exercise. It's getting towards vigorous physical activity. It's exercising a large number of muscle groups in the body, and it goes on for a significant period of time.

Norman Swan (6:37)

Depends on who you are, Norman. I'm not running that far.

Mark Humphries (6:40)

Well, I'm not running either, but that's because I've got osteoarthritis of the knee. So I've lost that ability to run. Once I've got quite severe osteoarthritis, I don't run anymore because it makes it worse. But I've actually been able to rehabilitate my knee so that I've actually got almost no Knee pain compared to a couple of years ago when I thought I was heading for a knee replacement. We can come back to that later. Enough of personal stories. But they've done big studies. So first of all, you become physically fit, your muscles strengthen, the pounding on the pavement strengthens your bones. So if you want to prevent osteoarthritis, you want to do weight bearing exercise and you want a little bit of impact on the bones in order to stimulate bone growth. And that strengthens up your whole musculoskeletal system. The idea that you wear down the joints comes from research which shows that if you're an elite athlete, marathon runner, there is a bit of damage to the joint after the run, but that also heals itself. But for the everyday runner who's not trying to win a gold medal at the Olympics, it's not convincing that there is any permanent damage at all to the knee. And there's a fair bit of evidence that in fact you do benefit from increased blood flow. I mean, this is a part of your body, these weight bearing joints, where there's not a lot of blood supply. And you want to actually have a healthy circulation of what's called the synovial fluid in the joint. You want reduced inflammation. And in fact, exercise reduces inflammation in your body. And for every kilo of weight that you lose, the pressure on your joints reduces. So the problem with knee pain can have a relationship to exercise because if you've played rugby or netball and you've injured your knee, that knee is more susceptible to knee osteoarthritis. But it's the injury rather than necessarily the exercise.

Norman Swan (8:39)

It's interesting sort of talking about athletes. Oftentimes research like this does look at elite athletes because for starters, they're groups that you can cluster together. You can, you can measure them and you sort of think like these people are in peak physical fitness. But actually it sounds like recreational runners are a better group to study. If we're trying to think about how you or I or someone listening here can improve their overall health rather than sort of like peak performance. And there have been some studies on recreational runners.

Mark Humphries (9:08)

Yeah, and there's a big Australian study looking at running and prospectically following people for about 15 years, it hasn't published its results for a while. It's called the Halo study. So some researchers would say this is not a conclusion that you can make definitively at the moment. I sounded very definite about what I was saying earlier, but the balance of evidence is on the side of exercise and running rather than Avoiding it because you're worried about your knees.

Norman Swan (9:35)

So with knee damage and running, there sort of seems to be a bit of a U shaped curve in terms of the X axis is the amount of running you do, say per week. And then the Y axis, the one going up and down, you've got your risk of knee osteoarthritis. And so on the very left hand side of the graph, you've got quite a large number of people not doing much physical activity. High risk of osteoarthritis, very low levels of osteoarthritis in the middle for people who are having like middling amount of exercise or running. And then on the right hand side, as you get into high volumes of training, that risk of knee osteoarthritis goes up again.

Mark Humphries (10:06)

Yeah. And a lot of people in this area who've looked at it say the U shaped curve is valid here. So there's a sweet spot for exercise. Now, for people who listen to our sister point podcast, the Health Report, you'll know that we are a bit skeptical about U shaped curves and J shaped curves because the people on the left hand side of that curve who are not getting any exercise and are at high risk of osteoarthritis, any U shaped curve, that group is not doing very much, like for instance, not drinking very much, not exercising very much, are often sicker on average than the people on the rest of the curve.

Norman Swan (10:42)

Well, the reason they might not be doing much exercise is because they already have knee osteoarthritis.

Mark Humphries (10:47)

That's true, although it's supposed to be correct, corrected for that. But they also may be heavier and therefore their weight is increasing the risk of osteoarthritis, not just because of the pressure on the joint, but also because when you are overweight or obese, you are in a more inflammatory state in your body and therefore you have a metabolic effect on the joints as well. And at the extreme end of the scale, when you're getting towards elite athletes, there may be an element of injury there. You've fallen over, you've hurt yourself, you've got caught up in a ruck or what have you. And therefore it's the injury that's the problem rather than the exercise. But it looks as though there may be a sweet spot.

Norman Swan (11:28)

Okay, so you've gestured at a couple of things I'd like to unpack a little bit. And one is what is actually happening inside your knee when there's knee osteoarthritis. And I think I had Always thought about it as being like the mechanics, the traumatic, like an injury or that wear and tear. Like you say that it's sort of like a physics is at play here, but then you talk just now about the inflammation side of things. How much is knee osteoarthritis about inflammation and your metabolism and how much is it about physics?

Mark Humphries (11:55)

Orthopedic surgeons have often thought in the past that it's about grinding your knee to dust. And they'll say, oh, when you've got the MRI scan, it's bone on bone, you're told, and it's terrible. It's bone on bone. We need to fix it up with a knee replacement. And I'm having a go at knee.

Norman Swan (12:11)

Surgeons here because you're really sticking the knife in.

Mark Humphries (12:13)

Because when you've got severe knee pain and you're really disabled with it and you're waking up at night with it, a knee replacement is a very good operation. The trouble is, for a lot of people who get a knee replacement, they still have some residual disability and residual pain. It's unusual to get to be completely pain free. So if you've not had much disability or pain and you have a knee replacement, you might be unhappy with it because you're still left with stuff. Whereas if it's really at the extreme end, and a lot of knee surgeons these days will say, come back and see me in two years time, it's not bad enough yet to need to have a knee replacement, which is the responsible way to do it. So it's a balance there. It is a good operation. To answer your question, that's the old way of looking at it. You're grinding your knees to dust, you haven't got any cartilage left. It's wear and tear and that's what's causing the osteoarthritis. And it's simply not what osteoarthritis is. It used to be thought there's no inflammation there, there's no role for the immune system. And it's now known that osteoarthritis is an immune condition. It's not autoimmune, but your immune system is involved and you do get inflammation in the joint and in the lining of the jo, you do get fluid in the joint and your general metabolic state can make it worse or better. So if you are in a pro inflammatory state, you are more likely to get inflammation in your joint and that inflammation in your joint could damage the joint and therefore cause the arthritis. This is not well understood, but inflammation is A core part of the process.

Norman Swan (13:45)

Which is why you said before that running is really part of the metabolic process, which means it can be part of the treatment. You mentioned earlier that there's a sweet spot. I know you sort of poured a bit of context on the U shaped curve, but let's say we'll stick with that just for a second. Where is that sweet spot for most runners?

Mark Humphries (14:03)

Look, the answer is nobody really knows. But if you're doing 150 minutes of moderate exercise a week and your aerobic part of that is jogging, it's unlikely to be doing your knees any harm if you haven't got any pre existing injury problems in your knees. And people who talk about rehabilitation of the knees, one of their aims is to get you at least walking and walking quite fast once you strengthen the muscles around the knee and stabilize the joint. But coming back to the metabolic side of osteoarthritis, if it's all about weight bearing, why do people get osteoarthritis in their hands?

Norman Swan (14:37)

Oh, I was not expecting to talk about hands in this episode about running.

Mark Humphries (14:41)

There is an incidence of osteoarthritis of the hands. And they're not jogging on their hands. They're not doing handstands here, which gives the lie to the fact that it's all about wear and tear. It's complicated, but it's thought that one element, osteoarthritis of the hands is the metabolic effect of inflammation on the joints independent of weight bearing. And I think they have done studies looking at runners comparing their hand osteoarthritis with their knee osteoarthritis.

Norman Swan (15:11)

What do they find?

Mark Humphries (15:12)

So this study, it's a small study, about 70 people, 35 people who were runners, 38 controls, they were in their early 60s and they paired them up as much as they could be possibly paired. And they had X rays done of their hands, their lumbar spine and their knees and followed them for five years in both the runners and the control groups. And what they found was that with time, 13% of everybody developed osteoarthritis of the hands and 12% of all people in the study developed osteoarthritis of the knees. So it's ixy pixie here. Running did not. In this small study, running did not accelerate the development of osteoarthritis of the knees. But simple aging created problems in both their hands and their knees.

Norman Swan (15:57)

So we've Got Ben with 20k run under his belt, eating his bowl of pasta. Doesn't mention any knee pain himself. So I'm guessing he's in fairly good condition. Does the fact that his parents and grandparents have had this pose a big risk? Like what is our non medical. Please do not consider this binding health advice to someone like Ben.

Mark Humphries (16:16)

Well, if I were to channel Professor David Hunter, who've had on the health report many times, he's doing himself a lot of good and that's exactly what he should be doing. When he's got a family history of osteoarthritis, he's doing the right stuff to prevent it.

Norman Swan (16:28)

Good on you, Ben. Norman, I know that you have resisted having a knee replacement for many, many years now. And it sounds like you're actually doing pretty well. What did you do? Because you were running, you were running pretty regularly up until a few years ago. What did you do to keep this surgeon at bay?

Mark Humphries (16:45)

So what I've done is I am fully invested in the process of rehabilitation of my leg as a whole. So one of the mistakes that people make about knee pain and their knees is they the quadriceps are the only muscles that count. It turns out that when you've got a weak joint, all the muscles in your leg matter, from your toes right up to your hip and your lower back. And so what I do is I go through a program. First of all, I cycle a lot and I cycle hard. I go to the gym and I do progressive weight training trying to strengthen these muscles. And I do Pilates twice a week where I do a lot of balancing core muscle activity and really stressing the muscles that you want to have stable in this situation. So what that's done for me is relieved the pain in my joint. What it's not done for me is got rid of the limp. So people see me limping in the abc, oh, what's wrong with you? Blah, blah, blah. And that limp's probably more of a habit than anything that I need to train myself out of. So people looking at me limping think I'm in pain, but I'm actually not in pain and I don't wake up at night. So I'm in pretty good shape. Although it is a progressive disease and one day I probably will need a joint replacement. But at the moment, I think I'm in pretty good shape.

Norman Swan (18:04)

But if it's inevitable, why not get it earlier?

Mark Humphries (18:08)

Well, I just don't believe in getting surgery done when you don't need it. There's always a complication risk. But it's hard work and it's much harder work than going to hospital for a couple of days and even having pain and rehabilitation for six weeks. It's much harder work rehabilitating and keeping it in good shape.

Norman Swan (18:24)

But for you it's worth it.

Mark Humphries (18:26)

Absolutely.

Norman Swan (18:26)

Well, Ben, thank you so much for the question. We love getting your questions. You can send them to thatrashbc.net au which is also where you can send anything, any feedback that you have for us.

Mark Humphries (18:36)

So Jen writes in.

Norman Swan (18:38)

Jen writes in with something that I'm going to take on the chin, Norman, because I passed up an opportunity to talk about. I passed up an opportunity to talk about brain worms and I'm very deeply sorry for this.

Mark Humphries (18:50)

Yeah, so Jen says I refer to the program regarding allowing dogs to lick faces. In Australia in the 1950s, high tattoo disease, dog tapeworm was passed to humans from dogs. Sheep growing areas were particularly affected. So certainly don't allow a sheep to look you in the face. And death from hydada disease or required major liver operations and that was not uncommon. And my husband had a relative who died from heatitude disease as children at the time. This resulted in most of us having drummed into us to never allow a dog or any animal to lick our face and always to wash hands after touching an animal. Hydatids have largely been forgotten but still exist in the feces of dogs who may or may not been treated for tapeworm. And we all know how dogs wash themselves once again. I guess education is the key. This is where we depend on the ABC to pass on the right mystery. Love your shows, both of them.

Norman Swan (19:41)

Great point, Jen. And without making too light of the fact that it sounds like Jen's family has been touched by this disease. It is pretty rare in Australia these days. I had heard of this before. As Jen says, hand hygiene, regularly deworming dogs, keeping dogs away from dead animals are all ways that you can protect yourself from this rare disgusting risk.

Mark Humphries (19:59)

Keep your disgusting questions coming in. And our call was your call last week. I wouldn't have made this call but for people to send in their cat pics.

Norman Swan (20:10)

Cause Norman, you're a known cat hater. Norman, I think it's probably the thing you're most well known for these days is being a cat hater. And I thought that perhaps some fluffy photos of our friends or of our listeners, furry friends might sway you. And we've actually had a few.

Mark Humphries (20:26)

We had a few. And some of them are very cute, you'd have to say. But I did start scratching, you know, feeling itchy, allergic as I looked at them.

Norman Swan (20:34)

You can't transmit toxoplasmosis via a photo so they can't get in your brain. Brain or allergies, it's true. But I don't think we've seen enough cat pics yet to be. To be sure. So please keep them coming in and.

Mark Humphries (20:45)

Let us know whether you're happy for us to publish your cat photos on our website.

Norman Swan (20:50)

That rashbc.netau See, we can be ecumenical about our animals.

Mark Humphries (20:54)

Can we? See you next week.

Norman Swan (20:56)

See you then.