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The overall benefits of running, including improving musculoskeletal, cardiovascular, respiratory, and mental/emotional health, are very well accepted in the fitness and healthcare communities.
In fact, recreational running has been shown to decrease the risk of cancer, depression, and diabetes, among other conditions.
What has been more of a debate, however, is the long-term effect that running has on weight-bearing joints of the lower extremity. In fact, the question “Isn’t running bad for your joints?” is one of the more common questions asked by people who are on the fence about getting into running.
Because of the perceived ‘wear and tear’ associated with running, a major concern for people is that they will end up with arthritis in their knees and hips. While it has been shown that roughly 50% of runners get injured each year, with ailments such as plantar fasciitis, shin splints, and IT band syndrome, research has shown that arthritis in runners isn’t as prevalent as many people think.
The arthritis referred to throughout this article is osteoarthritis, also known as degenerative joint disease, and arthritis and osteoarthritis will be used interchangeably. This form of arthritis involves deterioration of the cartilage and changes to the underlying bone in the moving joints of the body.
The prevalence of osteoarthritis increases with age, and the large weight-bearing joints of the lower extremity, for example, the hips and knees, are commonly affected. While not all cases of osteoarthritis are symptomatic, pain, stiffness, and swelling of the involved joint are commonly seen in those with this condition.
Research from the 1980’s and 1990’s
Back when knowledge regarding the correlation between running and arthritis was scant, several studies in the 1980s and 1990s began to gain insight into this question. The conclusion of several studies, for example, “Is Running Associated with Osteoarthritis? An Eight-Year Follow-up Study” and “The effect of running on the pathogenesis of osteoarthritis of the hips and knees,” demonstrated no correlation between distance running and an increased risk of lower extremity arthritis.
This information started to shift long-held beliefs regarding the safety of running. Subsequent research over the next two decades took this a step further and expanded on our understanding of running and arthritis. These studies showed that running might actually have a protective effect on joint health.
Research from the 2000’s
The 2008 study, entitled “Long Distance Running and Knee Osteoarthritis A Prospective Study,” tracked 45 long-distance runners and 53 similarly matched controls between 1984 and 2002 through x-ray analysis in order to determine if the running group showed more osteoarthritic changes in their knee joints.
The initial hypothesis of the authors in the 1980s was that long-distance running might be associated with increased incidence and severity of osteoarthritis when compared to a similar cohort of non-runners. This hypothesis was based on the notion that running was likely to accelerate arthritis changes due to repetitive microtrauma to the joints. Prior to the initiation of this study, as stated earlier, research had shown mixed conclusions regarding the relationship of physical activity to osteoarthritis of the knee.
The results of this study surprised the authors. Despite the running group having a slightly greater prevalence of osteoarthritic changes compared to the non-running control group at the beginning of the study (6.7% vs. 0%), by the end of the study, the running group didn’t have a higher prevalence of knee osteoarthritis (20% vs. 32%) or more severe cases of knee osteoarthritis (2.2% vs. 9.4%) when compared to similarly matched non-runners.
These findings prompted the authors to conclude that long-distance running among healthy older individuals was not associated with accelerated radiographic osteoarthritis and that this data raises the possibility that severe osteoarthritis may not be more common in runners.
Research from the 2010’s
Nearly a decade after this article was published, another study, entitled “The Association of Recreational and Competitive Running With Hip and Knee Osteoarthritis: A Systematic Review and Meta-analysis,” looked at the same topic. This study is a systematic review, which reviews the findings of relevant studies, and included 17 studies involving 114,829 people. The results helped to further shift the narrative that running isn’t as bad on our joints as what was previously thought.
Using the findings from the included studies, the authors compared the incidence of hip and knee osteoarthritis in three groups: Recreational runners, Non-runners, and Competitive runners. The competitive running group included those who had participated in international competitions.
The incidence of hip and knee osteoarthritis in the three groups were as follows:
- Recreational Runners – 3.5%
- Non-Runners – 10.2%
- Competitive Runners – 13.3%
This data shows that running, up to a certain point, can actually dramatically decrease your chances of developing hip or knee arthritis. While the cutoff parameters between recreational and competitive runners in terms of running volume aren’t exact, they’re thought to be up to 15 years of running and running 57 miles per week.
Research on the Rate of Joint Replacements
Since joint replacement surgery is a common treatment for advanced forms of osteoarthritis when other treatment options have failed, it is interesting to look into the rate of joint replacement surgeries in runners. The study, entitled “Effects of running and walking on osteoarthritis and hip replacement risk,” looked into the relationship between running and the rate of hip replacement surgery.
The authors concluded that running significantly reduced osteoarthritis and hip replacement risk, in part due to running’s association with a lower Body Mass Index (BMI), which will be discussed later. Because joint replacement surgeries would tend to parallel the rate of arthritis, it is not surprising that these findings are similar to the conclusions from the aforementioned studies.
The findings here are profound, as they not only answer the question of whether or not recreational running results in an increased likelihood of osteoarthritis, but they also demonstrate that it can help protect joints from long term damage. While running was once believed to be an activity that was off-limits to those of increasing age, these studies showed that it might be a good idea to run recreationally in order to maintain joint integrity.
Why Does Recreational Running Lead to Less Arthritis Risk?
A logical question then becomes, “Why does running lead to less arthritis in the hips and knees?” It would make sense that the increased wear and tear involved in running would lead to the breakdown of these weight-bearing lower extremity joints and lead to an increased rate of osteoarthritis. Now that we have shown this not to be true, the next step would be determining the reason why. At this point, it appears that there are likely several reasons why recreational running is actually beneficial for joint health.
Regardless of which mechanism decreases the risk of arthritis in runners, however, it is important to remember the fact that it does.
SAID Principle
One reason is that the body will adapt to the stresses imposed on it. This concept makes up the ‘SAID‘ Principle (Specific Adaptation to Imposed Demands). For example, when you lift weights, your muscles will become larger and stronger, when you perform cardiovascular exercise, your heart and circulatory system increase their capability, and when you spend time at high altitudes, your body will acclimatize by increasing the production of red blood cells.
The SAID Principle can be applied to the cartilage in the weight-bearing joints of runners, and in the opinion of physiotherapist and running expert, Blaise Dubois is a reason why runners have a lower incidence of osteoarthritis. In the ‘Top Ten Running Myths’ section of his book “Prevention of Running Injuries”, he states:
“The cartilage in a runner’s knee is thicker and stronger than that of a sedentary person. This can be explained by the simple fact that the tissue has adapted to mechanical stress. As long as the stress is applied gradually and does not exceed the tissue’s capacity to adapt, positive tissue remodeling will occur. In other words, cartilage, a living tissue, will rebuild more than it will deteriorate.”
Research into the relationship between running and joint cartilage, known as articular cartilage, is consistent with the opinion of Blaise Dubois. Several studies have been conducted on the effect of running on articular cartilage in animals, for example, Intensity-Dependent Effect of Treadmill Running on Knee Articular Cartilage in a Rat Model.
The conclusion of this study was that articular cartilage could adapt to the mechanical stresses of physical activity.
It was suggested that running, up to a certain point, can maintain the health and integrity of the cartilage. They stated that there is a limit to the safety of this activity, and stress above this limit can damage cartilage. While this cutoff point is difficult to define and likely has a large variation between individuals, it is consistent with the fact that elite runners have a greater prevalence of arthritis compared to recreational runners.
Lower Body Mass Index (BMI)
Another reason why running may be protective against arthritis is that it helps to maintain a lower body weight, which has been shown to be protective for hip and knee osteoarthritis. While this doesn’t account for the increased risk of arthritis in elite runners, it is likely a contributor for the decreased risk of recreational runners compared to more sedentary individuals.
Research has shown that for each pound of weight loss, it can reduce the stress on the knees by about four pounds and the hips by about two pounds. Less pressure on these weight-bearing joints results in less wear and tear and a lower risk of arthritis. Several studies have found that, among other risk factors, having a lower Body Mass Index (BMI) showed the greatest correlation for not developing hip and knee arthritis.
Maintaining a healthy weight, which can be aided by running, can also reduce inflammation in the body. This is important because inflammation is another known risk factor for osteoarthritis.
Overall Force Per Stride
A third reason is a bit more technical, but it is also very important. If you ask most people if walking or running places less stress on the lower extremities, walking would be the obvious choice. This answer is true in terms of peak load per stride, which is the highest level of stress placed on the bones, joints, and muscles when the foot is in contact with the ground.
Certain characteristics of running, however, make the average load accumulated per stride comparable to walking. This was a proposed mechanism for the lack of correlation between running and arthritis in the study Joint Loading in Runners Does Not Initiate Knee Osteoarthritis. We’ll begin with peak load per stride. During the single-leg stance phase of running, when one foot is in contact with the ground, you have the force of about 2.5 times your body weight placed on your leg.
For a 150-pound runner, this equals 375 pounds of force and is much higher in running than in walking. The average load accumulated per stride, however, is similar whether you are walking or running. This is because the ground contact time, the total time that the foot is in contact with the ground, is much shorter when running. In fact, for a runner who logs a 9-minute mile, the average ground contact time is less than 0.3 seconds, far shorter when compared to walking.
Therefore, the shorter ground contact time at a higher force observed in running may be similar in terms of overall force per stride as a longer ground contact time at a lower force, seen in walking. This research may help change the narrative that walking is much better on lower extremity weight-bearing joints when compared to running.
The results of research conducted over the past several decades are profound and have created a paradigm shift for many healthcare and fitness professionals, as well as lay people, who previously believed the misconception that if you run, you will get arthritis.
In addition to being a great exercise for overall health, the evidence suggests that recreational running is beneficial for hip and knee joint health, and is an activity that can be safely prescribed for most individuals. While this doesn’t mean that if you run, you won’t get arthritis, it helps to shed light on a previously controversial topic.
It may take years for the information from these studies to become mainstream and widely accepted; however, the time will come when people are taking up recreational running in order to protect their joints in the same way that they currently do with other activities such as walking, swimming, and cycling.
References
Is Running Associated with Osteoarthritis? An Eight-Year Follow-up Study
https://pubmed.ncbi.nlm.nih.gov/19077939/
The effect of running on the pathogenesis of osteoarthritis of the hips and knees
https://pubmed.ncbi.nlm.nih.gov/4028541/
Long Distance Running and Knee Osteoarthritis A Prospective Study
https://pubmed.ncbi.nlm.nih.gov/18550323/
The Association of Recreational and Competitive Running With Hip and Knee Osteoarthritis: A Systematic Review and Meta-analysis
https://pubmed.ncbi.nlm.nih.gov/28504066/
Effects of running and walking on osteoarthritis and hip replacement risk
https://pubmed.ncbi.nlm.nih.gov/23377837/
Intensity-Dependent Effect of Treadmill Running on Knee Articular Cartilage in a Rat Model
https://www.hindawi.com/journals/bmri/2013/172392/
Joint Loading in Runners Does Not Initiate Knee Osteoarthritis
https://pubmed.ncbi.nlm.nih.gov/28145908/
