Osteoarthritis and running
A lot of people are afraid of recreational running, as they believe they can hurt their joints (mainly the knee joint). There is a misconception out there that loading and using the body will cause excessive wear and tear, which in turn will lead to Osteoarthritis. Read on, because the whole picture is far more complex than that.
Key points
- Osteoarthritis is a joint disease where the cartilage in the joint is deteriorating. Many people believe that loading, such as recreational running, causes OA.
- The body is a living organism. Unlike a car, normal usage won’t wear and tear on the body. On the contrary, it builds it stronger!
- Movement and loading will supply the cartilage with nutrients to keep it healthy. An inactive lifestyle means that the cartilage won’t be as nourished, and can become weaker.
- There are many different things that can cause OA, such as lifestyle choices, genetics and previous injuries. Load isn’t the main reason.
- Overdoing load can play a role in the development of OA, but it takes a lot of load before it can negatively impact cartilage. Normal, recreational exercise and running has been shown to protect cartilage and keep it healthy!
Loading the cartilage will nourish it
Osteoarthritis is the name of a joint disease where the cartilage in the joint is deteriorating. Inflammation occurs in the joint and the disease causes changes in the bone. There is a belief that common use, such as recreational running, can cause deterioration of the cartilage in joints. However, more and more research indicates that recreational exercise might actually protect your cartilage, and even slow the progression of deterioration. Counterintuitively therefore a sedentary lifestyle, placing less impact on the joints, might be one of many causes to the development of Osteoarthritis.
To understand why normal use such as recreational running is not causing osteoarthritis, we need to learn a little more about how the cartilage works.
Your body is a living organism
If your car engine breaks down, you need to take it to the mechanic to get it fixed. Sometimes, the engine has to be replaced. The car is a machine, inorganic, it is not living, and so it cannot repair, regenerate, heal or grow on its own. Usage of a car will cause wear and tear on the components over the years, so after you’ve driven a certain amount of kilometres, parts will reach the end of their engineered life and need to be changed because they’re worn out.
Another perspective is if you break a branch off a tree or pull some leaves out, the tree will grow out new parts to replace it on its own. That’s because the tree is a living thing. Provided it has the conditions to sustain life, such as water, sunlight, nutrients and the right temperature, a plant will grow, change and adapt to the surrounding environment, including regeneration of damage. A machine such as a car cannot do that.
The body is also a living organism, like the plant. With the right conditions (and within obvious limits), the body can heal by regenerating tissue and build to become stronger to adapt to the loads it is exposed to. But what are the conditions the body needs? Or, in this specific case, what does the cartilage need to be nourished and kept healthy?
The cartilage will starve without load
In all joints, there is something called synovial fluid. The synovial fluid contains nutrients for the cartilage, and removes waste from the cartilage. In order for the synovial fluid to enter the cartilage to deliver nutrients and remove waste, you need to load the cartilage. You see, the cartilage works a little bit like sponge. When you squeeze it (load the cartilage), you remove the old “used” fluid, and when you release, it absorbs surrouding (nutriend filled) fluid. When you lift your foot off the ground, you release pressure, and the cartilage absorbs synovial fluid.
If you are sedentary or walk and run very little, you won’t get the replacements of fluids to deliver nutrients and to remove waste. Without water and light, the plant withers. Without frequent change of synovial fluid, the cartilage “withers”. Osteoarthritis in the knees is actually often seen in sedentary people. You need to load the cartilage to keep it healthy and nourished.
All the tissue in your body (muscles, tendons, bones, cartilage) needs to be used and loaded in order to grow healthy and strong. You can probably imagine how your muscles would look after some weeks of bed rest – they gradually shrink and become weaker (muscle wastage). In this context, you should not think of your body like a car. Usage will not place wear and tear on us in the same way as it will on a machine like a car – we can adapt and grow stronger!
But what causes Osteoarthritis then?
There are many reasons that Ostoearthritis develops, and it’s most likely not just due to one reason alone. One of the most important risk factors seems to be genetics. Some studies suggest that as many as 40-60% of the cases of primary OA in the knees are caused by genetics (2). “Primary” means that the OA hasn’t developed due to some other injury or disease. An example of secondary OA is if you develop OA due to a knee injury in the past. Previous injuries can increase the likelihood of developing OA.
Excessive weight and obesity also appears to increase the risk of Osteoarthritis. It was previously thought that the load of the weight was causing the OA to develop. But, turns out, there might be more to it than just load. Interestingly, obesity is found as a risk factor that increases the risk of developing OA in the thumb, and we don’t load your bodyweight much on the thumb, do we? The full picture is still not clear, but it is a consideration that obesity might be linked to increased inflammation in the body, and OA is an inflammatory joint condition. There might be other considerations, for example so called “metabolic reasons” that obesity is thought to be a risk factor for OA, that is not linked to the load of the weight it self. So even though the mechanical weight increases load on your joints, the load alone doesn’t explain everything.
Overloading might increase the risk of Osteoarthritis
So, as we have discussed, load isn’t the main reason for developing Osteoarthritis, but can load cause OA? Well as it turns out, overloading can indeed be a factor despite multiple studies showing that load in the form of recreational running and recreational sports is healthy and protective for the cartilage (3).
But you can have too much of a good thing. There was conducted a study on “elite runners”, recreational runners and non-runners (sedentary people). They found that the prevalence of knee osteoarthritis was 13.3% in elite runners, 10.23% in non-runners and as low as 3.5% in the recreational runners group. We also know that OA is seen more often in people in heavy, manual professions and work that involves a lot of squatting and sitting on your knees over years. So, this suggests that overloading over a long time can impose a risk but before you think this is contradiction, please note that the load needed to increase the risk is very high, and weekly recreational running has indeed been seen to reduce both the prevalence and the progression of knee OA (1).
Keep running!
That’s why we want to encourage you to remain active and keep on running, even though you might fear that running is hurting your knees. You need a great deal of load before it can increase the risk of OA. Even elite runners undertaking years of intensive training aren’t certain to develop OA. The most likely conclusion is that there is a complex interaction between genes, overload, previous injuries, lifestyle and your individual biomechanics that will determine whether you go on to develop OA or not. Load will most likely not cause OA in isolation, at least not if your exercise is recreational.
If you have been told you do have a meniscus injury or have a non-chronic painful condition in you muscles, tendons, other soft tissue or bones, you might be interested in reading our article about Trigo programmes to rehabilitate your injury!
Some people worry about the surface, that running on asphalt/pavements will increase the risk of OA, but there isn’t research to back up such claims either. So, whether you choose to run on a treadmill, on the pavement or in the woods doesn’t matter. Your running is most likely protecting your knees, not hurting them!
REFERENCES
- Alentorn-Geli, E. et al (2017) The Association of Recreational and Competitive Running With Hip and Knee Osteoarthritis: A Systematic Review and Meta-analysis. Journal of Orthopaedic & Sports Physical Therapy Volume 41 Issue 6. Page 370-442
- Tim D. Spector and Alex J. MacGregor (2004) Riskfactor for osteoarthritis; genetics. Osteoarthritis and cartilage. Vol.12. Pages 39-44.
- Physiopedia. (without year). Runners and Knee Osteoarthritis [online]. From: https://www.physio-pedia.com/Runners_and_Knee_Osteoarthritis