Knee Pain explained

Eric-Olivier Sirois

Physiotherapist

April 30, 2022

Introduction 

Many of us will experience knee pain at some point in our lives. Whether that be by running, walking, sitting for too long or biking, knee pain will most likely bother you at some point. This article will focus on knee pain around or under the kneecap, as this is what most will experience. Kneecap pain is very common and shouldn’t be alarming at first. There are tons of potential explanations for knee pain causes, and most of them are easy to correct quickly. The purpose of this article is to help you determine what is the most likely source of your kneecap pain and give you the resources necessary to decide if you need to be seen by a health professional for your kneecap pain and, if so, where to seek the appropriate help.

Patella-Femoral Pain (PFPS)

Kneecap pain is often referred to as PFPS or patella-femoral pain syndrome. To put it simply, PFPS is a pain in the region where your kneecap is. PFPS is an umbrella term meaning it isn’t in itself a diagnosis. It is a term that englobes certain symptoms but isn’t associated with a specific condition. It is usually diagnosed when the other common diagnoses were confirmed to not cause the pain, for instance, ligament sprains or meniscal tears. 

Anatomy 101

Let’s take a quick look at the anatomy of the knee joint. A joint is the intersection between two bones, so where ‘two bones touch each other’. Our knees are made of 2 joints: the patellofemoral joint and the tibiofemoral joint. 

The first is the joint where we have the kneecap (patella) sliding over the thigh bone (femur). The second joint is the one that most people think of when they talk of the knee between the thigh bone and the tibia. Our kneecap glides over the femur in a little groove that allows for smooth movement. The kneecap moves with the help of our leg muscles (quadriceps). The quadriceps attach to the kneecap, and so when we contract our quadriceps, we pull on the kneecap. This pulley system is well built.

Here is also a nice simple video that shows how the kneecap moves when we contract specific muscles and why the kneecap is so precious to us. 

Common Reasons for Kneecap Pain   

There are subgroups to PFPS that allow us to group according to the most likely leading factors of the symptoms. There are three main subgroups to the PFPS diagnosis. These are associated with different causes of the symptoms. All three groups have kneecap pain but different causes for the pain. This is important to understand as it will allow us to be more specific in treating the symptoms.  

For example, there are multiple reasons why someone may experience chest pain. Some people will have chest pain because of gastric reflux, and some because they have a heart attack. If both receive the same treatment, the odds are you won’t get the results you were looking for 50% of the time. 

In the same way, many potential factors could be causing your knee symptoms. You wouldn’t want someone to treat your chest pain blindly and follow a one-size-fits-all chest pain medication. In the same way, it would be irresponsible and dangerous to treat all kneecap pain the same way. Even if you have the same kneecap pain as your friend had three months ago, doing what he did is not the greatest idea as maybe the source of the pain is not the same. This is why it is important to seek professional help to receive adequate treatments. 

Acute Overload 

The first common cause of kneecap pain is known as acute overload. This is what happens when you do too much too fast. This is typically what happens to those who decided to start running as soon as the snow began melting and tried to get back to the old training they were doing at the end of last summer. The issue is that if you haven’t run in 4 months, your body is in no shape to do what it used to do when you were regularly training. What is happening is that you are stressing  certain structures too much, for instance, tendons. Your muscles haven’t been used this way in months, so they need time to adapt and recover. If you start too strong and don’t rest enough, your tendons will see this as overworking, and no one likes overworking. 

The Typical Presentation of Acute Overload(1)

Referred Pain

Another very common yet significantly underestimated source of knee pain is the lower back (as been shown to be at least the source 26% of the time)(3). I know this sounds very unusual, having knee pain because of your lower back, but it is true. This is likely your case if you are experiencing back pain as well. This pattern is known as referred pain. This is equally common in most extremities pain (shoulder, elbow, wrist, hip and ankles)

 Most of us know that one of the symptoms when you have a heart attack is left arm pain. But did you know this pattern occurs with a lot of body parts? The same is often seen in back problems. Referred pain means that you experience pain in a body region (x) while the problem comes from a second body region (y). This is possible because sometimes (x) and (y) have the same nerve. So, the information gets mixed up, and by the time it reaches our brain, it is impossible to know where the pain signal came from. Let’s picture it with an example.

We have two water streams that merge (as seen in the picture). As you can see, one stream is nice and clear, and the other one is all muddy. When they merge, the water still looks somewhat muddy. In our body, our lower back and knee mimic the same Y. There is information (clear water) coming from the knee receptors and some information that comes from our lower back receptors (muddy water). Here comes the issue. Your knee and lower back both have the common final stream to conduct their information (water). This means that the information that gets to the brain is a mix of clear and muddy information (no pain and painful information). As amazing as our brain is, it cannot determine if the mud came from the lower back or came from the knee. It only knows that the final stream is a little muddy, and that’s not good. 

In response to seeing that, the brain will send a painful signal to both body regions. It wants to make sure that it doesn’t miss where the pain is, as this could have important consequences. 

Similarly, you need an electrician to tell you if it’s the wall plug or the kitchen appliance that is not working. In your case, you need someone to determine if your knee pain is from your knee or your back. This is where a physical therapist can be extremely helpful as they are the professionals with the best tools to determine where the pain comes from in such a situation.

The Typical Presentation of Referred Pain in the Knee

Why Do My Knees Hurt When I Sit? Why Does it Hurt When I’m Not Moving?

As we’ve just mentioned, sometimes knee pain actually comes from our back, at least 26% of them according to Rosedale’s study. It is believed that most often, when pain suddenly appears or increases in the knee while someone is sitting or resting and not using their knee(s), that the pain is related to a spinal source (back). It is very unlikely that a joint would hurt in a non-bearing (not putting weight on it, for instance when we are sitting) will hurt if the origin of the pain is in the knee, since the knee is not being “used”. 

If the origin was for instance arthritis, it would most likely hurt less when sitting, since this would relieve some of the pressure from the joint. 

If the pain was caused by a muscle, when sitting, the muscles acting on the knee are pretty inactive which makes them unlikely culprits for the arising pain at rest. 

If the cause was acute overload, it would be very unlikely that resting the knee would increase the pain felt, as the way to treat acute overload is to decrease the stress we place on the joint and the surrounding structures.

Thus, when pain arises from sitting, referred pain from the back is a more likely culprit. It isn’t impossible that the aforementioned reasons could be the cause for increased pain when sitting, but they are not as likely as referred pain. 

A quick way to further correlate the back with the knee would be changing the posture of your back when sitting, for instance going from slouched to upright. If doing so seems to alleviate or worsen the pain, it would allow us to further lean toward a lower back source for your knee pain, since when only moving the back,  we are able to modify the way your knee feels. 

Why Do My Knees Hurt When I’m Walking? 

What about walking? Is it because I don’t walk properly? Usually, your feet or walking (gait) pattern are not the triggering factors for your pain, as you would’ve been experiencing pain for a long time since you’ve likely been walking pretty much the same way all your life. If you didn’t have an accident or surgery on your lower body or back recently, then the way you walk is likely not the culprit. 

The way we walk is unique to each of us. There is no such thing as a perfect walking pattern. There are so many factors that come into play that it would be absurd to focus on your gait pattern to treat your knee pain. The way you walk is usually optimal for your body. Everybody is different, and so is the optimal walking pattern for each of us. Just like that, we know that the problem isn’t walking in itself or the way you walk. 

There are a few potential reasons why it hurts when you walk. The most likely would be overload. Maybe you’ve been walking a lot more lately because you felt like you were getting out of shape. So you decided to start walking 10k steps per day every day even though you were walking 10k steps per week a week ago. Just like working out in the gym, if we are not progressive in increasing our activities, we will most likely hurt ourselves by overusing some tissues. 

Let's not forget that if you realized the way you walked changed recently, it is due to something and that is not how you walk. In such a situation, the change in your walking pattern is a symptom, not a cause of pain.

How Can I Correct It?

Acute Overload

You need to be mindful that you are not the athlete you were last summer (yet). Like with anything in life, you need to be progressive and control your training volume. Training volume means how many times per week, how long per session, and how intense you go in your sessions. You need to be careful with these variables so you don’t overwork your tissues at the beginning. The goal here is not to fully stop what you are doing but to be realistic and reasonable with your expectations.

If you aren’t very knowledgeable on volume management, you could cut your current volume in half. This means if you are running four times a week for 30 min at a moderate intensity, try going for four runs of 15 mins at moderate intensity. This should help give a chance to your body to recover and adapt to what you’re imposing on it. Then slowly increase by 10% every week as long as it feels good. 

If you realize your symptoms are coming back, then consider decreasing your volume again and maintaining this lower volume for a longer period. Maybe your body needs more time with a certain amount of volume to adapt, and that is perfectly normal. These recommendations are very simplistic. I would encourage you to seek professional help to program your return to sport properly. Physical therapists and athletic therapists, and kinesiologists are the professionals best equipped in this field.

Referred Pain 

With knee pain referred from the lower back, you will need guidance from a health professional. A physical therapist would be the best professional to seek help from first as they are the ones specialized for such conditions. A point to consider is that just like doctors, physical therapists are also specialized for different joints and conditions. It would be important to make sure you seek help from one that is specialized in back pain as often people will forget about referred pain and try to treat the knee even though the source of the issue originates from the lower back. 

The physical therapist will proceed with a thorough exam and make sure that the pain is linked to the lower back or not. If indeed the source of the kneecap pain is linked to the lower back, don’t be surprised if you leave with exercises for your back even though your greatest pain is at your knee. As the lower back gets fixed and treated, so will the kneecap pain.

Seeking guidance

If you feel like you would benefit from an evaluation to identify and treat your pain from a health professional, you are welcomed to take an appointment with me. It will be my pleasure to guide you and answer your questions. 

For more information, make sure to read my other articles which you can easily find on my profile.  To discuss the information disclosed in this article, or if ever you believe a statement is outdated or not evidence based, please feel free to reach out and let me know, I am always eager to learn. To do so, you can contact me by email at ericolivier.physio@gmail.com

References 

1. https://www.physio-pedia.com/Patellofemoral_Pain_Syndrome
2. Petersen, W., Ellermann, A., Gösele-Koppenburg, A., Best, R., Rembitzki, I. V., Brüggemann, G. P., & Liebau, C. (2014). Patellofemoral pain syndrome. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA, 22(10), 2264–2274. https://doi.org/10.1007/s00167-013-2759-6
3. Richard Rosedale, Ravi Rastogi, Josh Kidd, Greg Lynch, Georg Supp & Shawn M Robbins (2020) A study exploring the prevalence of Extremity Pain of Spinal Source (EXPOSS), Journal of Manual & Manipulative Therapy, 28:4, 222-230, DOI: 10.1080/10669817.2019.1661706

Pictures

1. https://wp02-media.cdn.ihealthspot.com/wp-content/uploads/sites/202/2018/02/03014828/iStock-664122448-1.jpg
2. https://nellmead.com/wp-content/uploads/2017/03/patellofemoralpain.jpg
3. https://twistedsifter.com/wp-content/uploads/2012/04/osijek-croatia-drava-and-danube-rivers-confluence.jpg?w=64