Is Running on a Treadmill Bad for Your Knees?

Running on a treadmill is part of daily exercise, you might wonder how bad is running on the treadmill for your knees? Running on a treadmill is not bad for your knees, and it may be safer than running outside. Running outside on variable terrain can add more stress and strain on your knees as it has to continually adjust to different levels of impact based on the terrain. A treadmill will make running easier for your knees than overground running because treadmill can offer shock absorption, which reduces the amount of impact and stress on the knees. Running on a treadmill will not worsen your knee pain or cause overuse knee injuries as long as you run with a proper posture and set the incline on the treadmill correctly.

Running on a treadmill is an excellent exercise for elderly people because they can run on their preferred speed which is adjustable on the treadmill and it has less impact on their knees. Although running outside on softer paths might seem to have the same benefit about reducing the impact on your knees, the stones and obstacles can still be the risk of twisting the knees.

Running on Treadmill vs. Outside

A research in 2019 has analyzed whether treadmill running is biomechanically comparable to overground running. 33 participants were included in this research to compare the differences between running on treadmills and running outside.

The key findings from this research indicated that muscle activity and muscle-tendon measures are similar between treadmill and overground running. The differences are appeared from the measures of foot strike, knee flexion range of motion and the vertical displacement (how much your body bounce up and down when running).

Researchers have found the following points which are reflecting that running on a treadmill produces a lower impact on the knees than running outside:

• The vertical displacement of running on a treadmill was significantly lower when compared against running on all overground surfaces
• In some situations, the characteristics of treadmill running biomechanics can be beneficial for training or knee injury rehab because treadmill has a less stiff surface which is preferable for rehab with lower vertical loading rates compared to stiff overground surfaces
• Higher muscle forces in the gastrocnemius and soleus have been found during treadmill running thus it may be suitable for rehab from lower limb stress fractures
• The Reduced propulsive force has been found during treadmill running which adds less stress on your knee joints because running speed (treadmill belt speed) is relatively stable
• Lower braking forces are found when running on a treadmill which produced lower impacts on the knees

Surface stiffness and impact on your knees

No matter you are running on the treadmill or outside, the impact on your knees from running is a dependent variable which is depending on the independent variable of the surface stiffness. The treadmill is slightly more comfortable for your knees than some of the other surfaces that we often come across when running:

• Concrete surface
• Grassy field
• Dirt field
• Rubber running track

A hard surface like concrete surface can cause higher impact or wear-and-tear on your knees if you don’t run in a proper posture. Running on a grassy field or dirt field has less impact on your knees but you might sprain your ankle if the surface is not flat or well maintained. Rubber running track is the ideal surface for running because it has an excellent grip, and the surface is relatively soft with less impact on your knees.

Similar to rubber running track, the treadmill deck, also known as the track or running surface, is also a great surface for you to run without causing too much impact on your knees. Because the upper side treadmill belt is made of high-quality PVC rubber and the underside is made by cotton, mono-filament and polyester which can provide excellent grip to both your shoes and the treadmill desk.

The cotton from the underside of the treadmill belt can help to reduce the impacts on your knees when running. Hence treadmill is well-engineered for running and pretty safe for your knees by comparing with other surfaces in the natural environment or man-made hard surfaces like concrete.

Choosing the right treadmill belt with more comfort

Choosing the right treadmill belt can actually offer your legs and knee joints more cushioning and comfort.  Treadmill belt thickness is the main factor that is directly related to the level impact on your knees and whether you can run comfortably on a treadmill. The treadmill belt is the component of the treadmill that the runner is directly contacting their feet.

Hence how much grip the treadmill belt can provide or how much impact it will cause to your knee joints are the main factors you need to consider when choosing the right thickness for the treadmill belt. Treadmill belt can typically be categorized in three different types based on its thickness:

• Single Ply: The treadmill belt is made by a single piece of rubber
• 2-Ply: The upper side of the treadmill belt is made by high-quality PVC rubber and the underside is made of cotton, polyester and mono-filament
• 3-Ply: Added an additional layer of rubber to provide “cushioning”

Treadmill belt with 2-Ply is generally the sweet spot for running because it’s made by high-quality PVC rubber which can give sufficient grip when you are running and the cotton from the underside helps to reduces the impacts on your knees. Cotton can also reduce the noise from the deck when the treadmill is operating.

Treadmill belt with 3-Ply may not be a right choice because the additional layer adds additional weight for the motor to operate which has a negative effect on the durability of the motor. Most importantly, the extra layer can make the treadmill belt become too soft to run and harder for you to maintain a proper posture which can add unnecessary stress on your knees.

Knee pain on the treadmill but not outside

Some people might experience knee pain when running on a treadmill but not outside. Generally speaking, the treadmill offers a better grip when running than most of other surfaces outside and it also provides shock absorption.

However, you might get tighter calves when running on the treadmill because of the fatigue which is causing by running on a constant speed without having a chance to change your pace or speed. Muscle fatigue could cause discomfort or stimulate existing knee injuries to cause knee pain in some situations.  

Anther reason might cause knee pain when running on a treadmill is that people tend to lead leg from fully extending which can cause the force from the treadmill to jam against their locked knees. Experts have suggested people to make sure the foot is landing under, not in front of the body when running on a treadmill.

Does the incline on a treadmill hurt your knees?

Does the incline on a treadmill can actually hurt your knees? Is running uphill on a treadmill bad for knees? The answer in short is no. Having the treadmill set on a low-to-zero incline is not good for your knees or legs. Studies show that tread belt propels a person forward thus people tend to land the foot in front of the body which can jam against their locked knees to cause knee injuries.

A Scottish expert, Philip Riches also confirmed running on a treadmill with no incline can make the runner tend to run with their knees very straight. The knees cannot absorb impact properly when they are in a straight position.

A simple way to prevent this is to set the incline on the treadmill for +1-2% to simulate overground running. Therefore, your knee can land naturally under your body to run on a proper posture. Hence running with 1-2% incline on a treadmill will not hurt your knees.

Myths about Running on the Treadmill

Many people think they will get overuse knee injuries because of the constant repetitive motions from running on the treadmill. The reality is that running on the treadmill is actually easier for your knees than running outside because there are no obstacles and treadmill belt is a shock absorber to reduce impacts on your knees.

Running on a surface like concrete is harder for your knee joints than running on a cushioned surface like the treadmill belt. Other surfaces like a grassy field or dirt field do not provide sufficient grip for running which can put more stress on your knee joints and you might encounter obstacles to twist your knees.

Tips for Protecting Your Knees When Running on a Treadmill

Many running instructors have suggested that adding incline reduces certain forces on the knees and it can provide additional comfort when you are running on a treadmill. While the suggested incline on a treadmill to mimic natural overground running is +1-2%, there’s no perfect incline for everyone. It’s a trial and error to find what incline on a treadmill works better for your knees as long as it’s within a reasonable range.

Running at a zero incline is definitely not doing your knees a favor because 0% incline on a treadmill is actually simulating downhill running which adds a high strain on your patellar tendon and knees.

As we mentioned in the previous section, a treadmill is propelling your body forward whereas you need to overcome the resistance when running outside. If you set a zero incline on a treadmill will cause your muscles to work harder to control your movements to balance your body so you don’t fall. Too much muscle strain around the knee can be a contributing factor to overuse knee injuries.

The following tips will help you to protect your knees when running on a treadmill:

• Always set the incline on the treadmill to around +1-2% to simulate the conditions such as resistance when running outside
• Try to make as little noise as possible. Quiet steps mean less impact on your knees
• Wear shock absorbing running shoes so the muscles and knee joints can absorb less impact
• Warm-up before running on a treadmill and cool down after running can improve the blood flow around your legs and knees before running and prevent muscles tighten quickly if you suddenly stop

Takeaway

Treadmills are especially useful to help you maintain a good running schedule during the winter because it can be cold outside. Treadmills are also very helpful in providing shock absorption when running to help to reduce the impact and stress on your knees. As long as you run on a treadmill with a proper incline between +1-2%, running on a treadmill should not hurt your knees and it’s a great exercise to strengthen healthy knees.

Running includes repetitive weight-bearing and motion that is beneficial for the knee joints. By choosing to run on suitable surfaces like a treadmill belt or running rubber track can help you to maintain knee health by exercising your body with a proper posture to avoid potential knee injuries. You can also check out our latest range of knee braces here if you are looking for knee braces for running.