For years, a persistent belief has held that running is a surefire way to wreck your knees. But what does the scientific evidence actually say? According to exercise scientists, the reality is far more positive, with running likely strengthening joints and being a viable activity even for older beginners.
The Science of Impact: Why Running Strengthens, Not Weakens
It's true that running is a high-impact activity. With each footstrike, the body absorbs a force equivalent to two to three times a person's bodyweight. This load does pass through the knees, which experience about three times more force during a run than during a walk.
However, the human body is not a static machine that simply wears down. It is a dynamic, living system that adapts and grows stronger in response to the stresses placed upon it. The cartilage in the knee joint is a robust, flexible tissue designed to cushion movement, and it actually requires load to stay healthy.
Research indicates that when load is removed—such as during prolonged bed rest—bone and cartilage begin to deteriorate. Conversely, studies show that runners tend to have thicker knee cartilage and better bone mineral density than non-runners.
Is There an Age Limit for Taking Up Running?
A common question, especially among older adults, is: am I too old to start? While specific studies on taking up running later in life are limited, related research provides strong clues.
A 2020 study focused on older adults aged 65 and over who began high-intensity jump training, known as plyometrics. This type of exercise places even greater joint loads than running. The participants not only found it safe and enjoyable but also saw measurable improvements in strength and function.
This suggests that starting a running regimen in later life can also be safe and effective. The key, experts stress, is to begin slowly. Muscles and joints need time to adapt to new demands.
A recommended approach is to start with walk-run intervals, gradually increasing the running duration over weeks and months. This allows the body the necessary time to build strength and resilience.
Managing Risk: How to Prevent Common Running Injuries
The myth of running being inherently bad for knees persists partly because injuries are common; nearly half of all runners experience one each year, with knee issues being frequent. Crucially, most of these are overuse injuries, caused by poor load management rather than the act of running itself.
To minimise risk, follow these three evidence-based strategies:
First, progress your mileage gradually. Avoid large spikes in distance or frequency. A good rule is not to increase your total weekly running distance by more than a couple of kilometres at a time.
Second, support your body with adequate nutrition. Running burns significant energy, and you need sufficient fuel—particularly carbohydrates and protein—to recover properly. Some research also points to the importance of calcium and Vitamin D in helping to prevent stress fractures.
Finally, consider your running surface. Evidence suggests that running on grass generates less impact than harder surfaces like concrete. Incorporating some grass runs into your weekly schedule, especially when starting out, can help your body adjust.
For the vast majority of people, the profound benefits of running for cardiovascular, metabolic, and joint health far outweigh the risks. By starting sensibly, progressing slowly, and listening to your body, running can be a rewarding part of a healthy lifestyle at almost any age.
