The main reason your knee joints hurt when you are running is most likely due to running with a heel strike, especially at faster running speeds of around 11 km/hr to 15 km/hr.
Why Your Knee Joints Hurt From Running
Here’s the thing, when runners heel strike, they typically straighten (unbend) their knee to allow the foot to strike the ground squarely on the heel. A straightened knee at touchdown during running amplifies the contact force up the leg. This also increases peak knee extension moment by 25% as the speed of heel strike running increases and this knee extension moment remains high during the stance phase of running as well (Peterson et al. 2014). The research on knee-joint function in heel strike running has demonstrated that the volume of mechanical stress may increase on the anterior portion of the knee which may lead to patellofemoral pain syndrome (i.e. runners knee).
To round out impact at the knee, make sure you land with a forefoot strike while the knee is softly bent and flexed. Because the knee is flexed in most non-heel strike landings, less impact is delivered to the body. Below is a video showing just how you should bend your knees at ground contact to reduce knee extensor moment.
If you bend your knees when you run on your forefoot, it will greatly improve your knee pain and knee-joint function. I was a heel strike runner, than I noticed that most elite distance runners as well as barefoot runners, don’t heel strike, they land on their forefoot and they bend their knees, too. So, I decided to give forefoot running a try, and it worked! I have no knee problems ever since I stopped heel striking when I run.
Need more convincing on how dangerous heel strike running is? Here are some of the injuries that are proven to be caused directly by heel striking when you run.
More From Run Forefoot:
BSc Neurobiology; MSc Biomechanics candidate, ultra minimalist runner & founder of RunForefoot. I was a heel striker, always injured. I was inspired by the great Tirunesh Dibaba to try forefoot running. Now, I'm injury free. This is why I launched Run Forefoot, to advocate the health & performance benefits of forefoot running and to raise awareness on the dangers of heel striking, because the world needs to know.