First of all welcome to my second blog post! My name is Joe and I am a licensed Doctor of Physical Therapy and USA Track & Field running coach. I am also an avid runner, triathlete, and somebody who loves simplifying research to provide advice for endurance and strength athletes! I am excited to start writing new content for all my peeps trying to better themselves. Let's get straight into the topic of today which is " a simple trick to help with knee pain when you run".
Alright so I am sure all of you want to get right into it. What is the secret? How can I fix my knee pain? Let's all settle down for a second and take a few steps back (no pun intended). Before I tell you what I have used to help countless runners, including myself, rehab from running related injuries, let's take a dive into some other important concepts to understand before we get into new and exciting tips on how to help your pain!
Running and knee pain
Some metrics suggest that over 13.9 million people in the U.S. participate in running as a form exercise (1). This is a colossal amount of people! Due to the repetitive nature of the sport, running related injuries are an unfortunate reality. Incidence rates for running injuries are as high as 79% within any given six month period (2). No this doesn't mean that you are doomed to injury, but injuries happen and we should do our best to prevent and manage them. This is especially important when we consider how much force is placed on the body during running. A recent study suggested that 4.5-7.6 times the body weight has to be managed when running (3). This is why we need to consider how to alter these forces when joints like the knee are irritated.
Speaking on irritation, many individuals come into the clinic and they are looking for the "ONE SPECIFIC CAUSE" of their knee pain. I wish things were this straightforward. We are still developing an understanding of all the causes that can contribute to knee pain which include: kinematic abnormalities, reduced proximal hip strength, overuse, and excessive forces on the patellofemoral joint (3). With all of these factors competing as causes, it is important to have simple takeaways for runners that give them a streamlined approach to their recovery and also a way to stay active. Because at the end of the day, that's all runners really want. They want to stay active and keep running.
What is cadence or step rate?
If any of you use Strava, own a Garmin watch, or use an apple watch to track your runs, you probably get tons of numbers that come up. Some of them you may be familiar with while others you may not know their significance or meaning. An example of what you might see is pictured below.
Let’s be honest, this is overwhelming. Outside of knowing the temperature, which one of these should I care about and how does it impact my running? Well today’s blog post is all about cadence so let’s try and understand that one variable first.
Cadence or "step rate" to put it simply is defined as how many steps you take per minute. Most people don’t think about a specific number when running! You just go out with your headphones and running shoes and make it happen. But cadence is an important aspect of running because it really tells us how often your feet are coming in contact with the ground. Think about it this way: if you have a higher cadence (170-180 spm), you are taking more steps and they are shorter steps! This is why when you are running fast, your cadence naturally increases. Your legs start picking up like a finely tuned engine and the pistons really start firing. Some people may not even notice but their cadence could be a little bit on the lower end (130-150 spm). Is this a bad thing? Of course not. But what it means is that they take longer strides which means their leg is going to be more extended when they make contact with the ground.
Hopefully I haven’t lost you yet! So now we have:
1) a definition of cadence
2) how it changes with pace or speed
3) what it means if your cadence is on the lower end.
Why does cadence matter?
Here is where things get super interesting. So much research has gone into step rate manipulation as a way of managing running related injuries. It not only is a simple thing to change, but also a specific variable all runners can keep in mind when out on the road. So how and when do you change it? Studies have found that it is particularly helpful for managing knee pain in recreational runners. One study by Lenhart & colleagues found that increasing step rate or cadence by 5-10% offloaded the patellofemoral knee joint by 14-20% (4). The idea behind why this works comes back to the principles mentioned earlier about stride length, cadence, and the forces placed on the body. If your cadence is low then your stops are long and you are most likely contacting the ground with the heel. That means you are increasing the demands on the knee joint, and the quad muscles have to work overtime to keep that knee moving nice and smooth. By increasing your step rate (taking shorter steps) you are reducing the knee angle at initial contact and landing in a more flexed position. Heiderscheit & colleagues found that step length, COM vertical excursion, and horizontal distance from the COM and heel at initial contact were inversely related to step rate at both 5% and 10% increases (5). To put it simply, by increasing your cadence by 5-10% you are decreasing step rate and your foot is landing closer to the center of your body. What this does is allow your COM to be closer to the foot that is landing and thereby reducing some of that force being placed on the knee. Alright that's enough scientific jargon for the morning. Hopefully you get the concept by now. Let's move on to an actual example of what manipulating the step rate will look like.
Cadence Manipulation Example
So you go out for a run and your pace is 9:15 per mile and BAM you start having some knee pain. Hmmm that’s a little weird. You look at your cadence on your watch, Strava app, etc. and you see your cadence is at 152 spm. So what you do is start thinking about taking shorter steps but keeping the same speed. This will mean your cadence will increase from 152 spm to 160- 167 spm. Now maintain that cadence and see how you feel. Usually most runners will notice a difference within the first two miles. One caveat is that although this modification will put let stress on the knee, it will increase stress on the ankle. This is the natural balance of things. You cannot just make forces disappear. They can only be shifted to other places. So you would want to avoid using this approach of increasing cadence if you are recovering from an achilles tear, metatarsal stress fracture, or posterior tibial tendonitis.
Alright we accomplished a lot in a short amount of time! The big takeaways are:
Cadence is one of the many things you can easily manipulate with running.
Cadence is defined as steps per minute. The higher the cadence the shorter the stride length.
For those of you who have knee pain, increasing cadence by 5-10% can reduce stress on the knee by up to 20%.
Increasing cadence will put more stress on the ankle and foot so use this with caution.
Let me know what you think about this topic or if you have any questions you can comment below. Please share this blog post with a friend or fellow runner! We want to help out as many active individuals as possible. Like, comment, share, and happy running.
Keep Moving Forward!
Dr. Joseph Daigneau, PT, DPT
Owner of Persevere Physical Therapy, LLC
Reference articles:
1. Running USA. 2012 State of the Sport – Part III: U.S. Road Race Trends. 2012
2. Lun V, Meeuwisse W, Stergiou P, Stefanyshyn D. Relation between running injury and staticlower limb alignment in recreational runners. British journal of sports medicine. 2004; 38(5):576–80. [PubMed: 15388542]
3. Chen YJ, Scher I, Powers CM. Quantification of patellofemoral joint reaction forces duringfunctional activities using a subject-specific three-dimensional model. J Appl Biomech. 2010;26(4):415–23. [PubMed: 21245501]
4. Lenhart RL, Thelen DG, Wille CM, Chumanov ES, Heiderscheit BC. Increasing running step rate reduces patellofemoral joint forces. Med Sci Sports Exerc. 2014 Mar;46(3):557-64. doi: 10.1249/MSS.0b013e3182a78c3a. PMID: 23917470; PMCID: PMC3925193.
5. Heiderscheit BC, Chumanov ES, Michalski MP, Wille CM, Ryan MB. Effects of step rate manipulation on joint mechanics during running. Med Sci Sports Exerc. 2011;43(2):296-302. doi:10.1249/MSS.0b013e3181ebedf4
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