Each week, MyHealthNewsDaily asks the experts to answer questions about your health.
This week, we asked exercise experts: Is running bad for your knees? Their answers have been edited and condensed for space.
Dr. Lewis Maharam, fellow of the American College of Sports Medicine:
That's an old wives tale. Your parents decide if you're going to have arthritis or not you'll have arthritis — it's genetic.
Jogging, or running, itself will not cause the arthritis. If you already have arthritis, and you have bone and bone contact, and no cartilage in your knee, running will make it worse.
If you're doing harm to your knees, if you're running and jogging and the pain becomes such that it alters the way you run, then it's time to stop and go see your doctor.
In fact, running helps future arthritic patients actually be more active in their later years. The compressive motion, helps bring more fluid in your knees and keeps them moving.
Dr. Stephen G. Rice, Director of Sports Medicine at Jersey Shore University Medical Center:
Not everyone who runs is destined to get arthritis.
The knees take a lot of pressure. The hipbone is a very nice ball and socket, and the ankle is set up in a good way, but the knees can take nice, happy cartilage and start to break it down.
The condyles of the femur (thigh bone) are round, and rest on the flat surface of the tibia (shin bone). There is always a place where the two bones touch bone-to-bone (as a basketball on a table would do). Both of these bones have a coating of hard, shiny, firm cartilage at the ends, enabling the bones to glide on one another.
The C-shaped meniscal cartilage in the knee is more spongy — like your nose or ear. It helps stabilize the thigh bone on top of the shin bone, and provides cushioning as we run, jump or walk.
But over time, the meniscal cartilage can wear down and lose its sponginess, and thus not absorb as much shock. The bones then pound on each other harder, and from that friction, arthritis develops and worsens.
The lighter you are, and how well you land your feet are also important. Not everybody hits the ground with the same relative amount of force: Some people walk softly, and some sound much louder walking by. For those people who hit heavier, that extra force is an issue. Then there's the issue of whether people's weight is healthy.
So, yes you can begin to develop arthritis from the pounding from running. However, the person who is active and fit and moving around is doing the most active defense against arthritis. There's a happy medium between whether you run smart, slowly building up your endurance, and stay active, and if you put extra force on your knees.
Some people who are genetically set up for arthritis, and no matter how well they run, they will end up developing arthritis.
Chris Troyanos, certified athletic trainer and the medical coordinator for the Boston Marathon:
Inherently, running is good and healthy for most people, but it's a matter of how you get started in it, and it's a matter of slow progression.
However, there are body types out there that are not conducive to running. For example, people who are excessive pronators have the inside part of their feet drop inward more than it should when they're running. That causes stress on the feet and knees, so their bodies are naturally not great shock absorbers.
People who have hyperextending knees — technically the term is genu recurvatum — are also going to have trouble running. Those who have some of these issues can run, but they may not be able to run more than a mile or two.
When you're looking at starting a running program, one you might want to start with a walking program first, then make the leap to an easy running program.
As you go through these steps of increasing your activities, it's important to listen to your body. If you are getting knee pain when you go from 5 to 7 miles a day, that could be your threshold for you.
If you have any type of existing pain or discomfort in your legs, it's not smart to keep running.
Dr. Jon Schriner, faculty member at Michigan State University
The jury is still out. Some say yes running is bad for the knees, some say no.
It's well known that heavier people are at higher risk for arthritis.For every pound of weight a person carries – whether it's in their body or they put it on in a pack – they have four pounds on the knee when running. In other words, if you weigh 100 pounds, there are 400 pounds of force on the knee with each foot strike.
It can also depend on how the person is running: how high you lift your foot off the ground and how you strike the ground. Joggers tend to strike with less force, runners tend to have longer strides and put more force on the knee.
There are many other factors that go into how running can affect your knees such as weight, body structure, shoe selection, and technique – we refer to it as going too far too fast too soon.
I don't think there's enough evidence that says running within non-abusive limits causes arthritis. But then it's a question of what's abusive limits? We could say that running ultra-marathons could put people at risk, and new marathoners I see often run too far, too fast, too soon and end up with knee problems, but other marathoners don't have problems.
There are some people who say at that age 40 or 45, people should combine running with bicycling or some other cross training, so they're not just pounding their knees, and that seems to work well to keep people physically fit, cardio-fit and keeping the knees in action.
In general, if your knees are healthy and you follow a reasonable approach to running you should not injure your knees. If you have knee pain for any reason you should seek the advice of a qualified Sports Medicine Physician before it becomes serious.
Dr. Michelle Wolcott, associate professor at the University of Colorado School of Medicine:
If you haven't had an injury, a broken bone or a ligament injury where you are predisposed to arthritis, then your chances of creating arthritis are minimal.
We know that weight-bearing exercise, such as running, helps prevent osteoporosis and osteoarthritis. Repetitive weight bearing and motion are good for the joints, and running essentially does that.
Extra pounds may or may not make it harder on your knees when you run. If you have lean weight — and by lean weight I mean muscle weight — it will help support your joints and bones. But if it's weight from fat that is non-functional, it will just add stress on the knees.
Obesity definitely plays a role in osteoarthritis of the knees. When you put too much force on cartilage – a common place is underneath the knee caps – the pressure on your knees is greater. And that pressure on the cartilage will break it down over time. This is why obese people are more prone to osteoarthritis.
There is a huge genetic component to osteoarthritis as well. If you have a family history of osteoarthritis and have knee pain, running may not be the best exercise for you.
If you are not predisposed to osteoarthritis, and have healthy knees and are of healthy weight, then running doesn't affect your risk for knee arthritis. That's a huge misconception and one that I fight all the time. There's absolutely no evidence to the idea that running alone causes osteoarthritis. People who claim that running caused their knee pain often already had had injured knees.