How Do I Stop My Knees From Hurting When I Run?

Foot strike (how you land on your foot) when running can be a source of knee injury. Heel striking is the main cause of knee pain and injury, even causing permanent damage to the joint, regardless of cushioned footwear. Good news however, the knee was found (references below article) to be reliably and sustainably protected from mechanical stress and high impact by forefoot striking as landing forefoot-first was found to lower the tibiofemoral compressive forces and knee stiffness known for destroying the joint.

How Heel Strike Running Causes Shin Splints and Fracture — Runner’s knee, also medically called ‘tibiofemoral joint pain’ is primarily caused by landing heel-first. This is because at heel strike the knee is fully unbent which causes the knee to be unusually stiff, and locks the joint into an unstable position. At the same time, the unbending of the knee at heel strike facilitates an excessively long stride which causes the body to brake intensively because the center of mass (torso) collides with the planted leg for too long. Worse still, an unbent knee at heel strike was found to cause the leg to lose much of its shock absorbing capabilities, thereby amplifying impact across the entire body.

The knee is the most common site of injury in runners [1], especially in overweight runners, but these runners can reassuringly protect their knees and avoid injury by avoiding heel strike, and adopt a forefoot strike, (shown below) because forefoot striking eliminates the known mechanical variables responsible for knee pain.

Does Forefoot Running Hurt Your Knees? — Landing with a forefoot strike, which involves landing on the balls of the foot, not high up on the toes, makes the safest, most functional use of the knee by enabling it to softly bend and flex at landing. This improves the compliancy of the joint, making it better at absorbing impact, stabilizing the foot, while preventing chronic stress to the knee, and helps guide your entire stride to make it shorter, not longer like in heel strike running.

As for heel strike running, it causes the knee-joint to lockout at landing, facilitating an over-stride tied to more collisional and compressive impact, which was found to (references below article) increase the degenerative process of the knee-joint, regardless of the amount of under-heel cushioning in a shoe.

Worse still, the over-stride engaged by heel striking shoves your upper body farther back, causing more of your body weight to press harder down onto the knee, resulting in greater mechanical stress and loading at the tibiofemoral joint [2], but this is not the case when a forefoot strike is used (shown below):

Is Forefoot Running Better for Energy Economy than Heel Striking? — Landing heel-first when running (above right), elongates your stride too much, resulting in an over-stride and a brake effect that persists for too long. It is during this excessive brake period where the body weight increases compression on the knee joint and also increases trauma on the tibiofemoral joint as compared with forefoot running (above left).

Bottom line, the more you weigh, the more stressful heel strike running will be for your knees, but forefoot running sustains the best, regardless of not just body weight, but running surface, meaning you can run on the hardest surface if you land with a forefoot strike you will not generate any more impact, but you will if you land with a heel strike.

In the final summation, foot strike pattern is extremely important because it directly influences your knee-joint mechanics. Forefoot running decreases compressive loading transmitted across the knee simply by decreasing knee extension and increasing knee flexion at touchdown as compared to heel strike running.

Even better, increases in knee flexion, engaged by forefoot striking, was found to provide a notable cushioning effect, while improving the knee’s shock absorption capacity at touchdown [3]. Furthermore, reduced knee extension in forefoot running also reduces the action of which the runner uses the knee-joint to propel the body upward and forward. This is why increased body weight is not a risk factor for knee injury in forefoot running -because increased knee flexion prevents the knee from being heavily loaded and augmented impact is neutralized via less time spent braking with the ground.

Last but not least, its not just the knee forefoot running safeguards from injury, your lower back is also more protected from injury with forefoot running than heel strike running. Read more on that here!

References:

[1]. Messier SP, DeVita P, Cowan RE, Seay J, Young HC, Marsh AP. Do older adults with knee osteoarthritis place greater loads on the knee during gait? A preliminary study. Arch Phys Med Rehabil. 2005;86(4):703–9.

[2]. Messier et al. Risk factor and mechanism of the knee injury in runners. Med Sci Sports Exerc, 2008; 40(11):1873-9.

[3]. Warren BL, Jones CJ. Predicting plantar fasciitis in runners. Med Sci Sports Exerc. 1987;19(1):71–3.

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