Approximately 50% of running-related injuries occur at the knee, many of which can be attributed to the inability of this joint to control the loads applied when the foot first hits the ground. Theoretically, if these loads on the knee can be reduced, injury rates can also be reduced. Step length is directly related to the amount of force transmitted through the ankle, knee, and hip.
A long stride length puts the foot way out in front of the body, where it acts as a brake every time it hits the ground. With this braking pattern, all of that extra energy travels up the leg and affects the ankle, knee, and hip. A shorter stride length has the foot landing closer to the body’s center of mass, reducing this braking force. A short(er) stride = decreased force through the knee! The easiest way to shorten stride length is to increase step rate, or cadence, without increasing speed. The internet will tell you that there is an ideal cadence (usually stated at 175 steps/min), but it is more realistic to make changes based on your comfortable starting point than to shoot for an arbitrary number.
A 2012 study demonstrated that increasing step rate 5-10% over participants’ natural step-rate dramatically reduced the forces transmitted through the leg, especially the knee joint. Faster step rate = shorter stride length = less force to the knee! Shortening stride length has resulted in a reduction in anterior knee pain, ITB syndrome, and shin splints/stress reactions of the tibia.
Give it a try! You don't need to be precise; when you're out on a run, try to subtly increase the number of steps you're taking without speeding up. Hold this new pattern for a few minutes, and then return to normal for comparison. If you’d like to be more exact, you can download a metronome app on your smartphone; find your baseline pace, and then dial it up 5-10%. A running analysis at Custom Performance may help you to adjust your steps! It is a mental challenge to break up your natural rhythm, but it may be a simple fix! It takes approximately one month for this increase in rate to become the “new normal,” so keep at it!
 

Andrew Ward SPT, CSCS Heiderscheit BC, Chumanov ES, Michalski MP, Wille CM, Ryan MB. Effects of step rate manipulation on joint mechanics during running. Med Sci Sport Exerc. 2012;43(2):296– 302.