Knee Pain: What You Kneed To Know
Ok, I know that was a bad joke… so thanks for reading this anyway! In my last post I talk about patellofemoral pain syndrome and IT band syndrome being potential diagnoses of a cyclist’s knee pain. They cause pain in different areas of the knee but are both caused by repetitive movement. You will hear me say this many times when I’m talking about pain or injuries in any part of the body. Injuries happen when you do more than what your body can handle. It comes down to a simple equation:
Demand > Capacity = Injury/Pain
Capacity > Demand = Injury/Pain
Demand refers to what you’re asking your body to do. The load or stress you place on your body when you work out, exercise or play a sport. Capacity is what your body is capable of doing. When I assess someone, part of what I need to figure out is which way their demand overtook their capacity. This can happen in a few different ways:
You do a small or “normal” amount of work, but your body isn’t well prepared and you have low capacity for what you have done. In this case, the person may be deconditioned, hasn’t done exercise in a while and picking it up again or perhaps is trying something new they aren’t prepared for.
You have good capacity but you’ve done too much. Here someone is well trained, ready for the activity, but perhaps they bit off more than they could chew. They could have been going for a PR (personal record) or training with someone a little bit stronger than them and tried to keep up.
You have good capacity and you do a “normal” or moderate amount of activity, but repeat this without enough recovery time. In this situation, even though your overall capacity may be at a certain level, after training or exercise your capacity is reduced for a short period of time while your body gets stronger and replenishes energy that was used. If you continue to load your body during that time, it may not be able to perform at the same level, even if you expect yourself to be able to. Without adequate recovery tools (time, sleep, nutrition) this period of recovery may be longer than usual. This would be where that overuse injury would happen. You might notice some soreness here or there during or after your activity and with time, this continues or gets worse. Overuse injuries are more common with activities or sport that require repetitive movements like running or cycling.
Today’s post will be focusing on common overuse or atraumatic injuries in the knee. I won’t be touching on any major knee injuries (ACL, MCL or meniscus tears) which more commonly happen in one moment in time. I will also be avoiding any growth-related pain or injuries which also tend to be overuse injuries but happen because of differences in the body while it is still developing.
PARTS OF A WHOLE
When we talk about a joint injury, we should separate the joint into different regions. Each region will be predisposed to a certain type of injury because of its anatomy, function and the stresses imparted on that area during activity. We can divide the knee into 4 different areas: anterior (front), posterior (back), medial (inside) and lateral (outside).
In the anterior region, pain can be caused by patellofemoral joint (knee cap), the patellar tendon or the fat pad under the knee cap and tendon (not seen in this image).
In the posterior region, pain can be caused by nerve tension from the tibial nerve (continuation of the sciatic nerve), the hamstring tendons or the calf tendons (these are less common) or a Baker's cyst (not seen in this image).
In the medial region, pain can be caused at the Pes Anserine attachment.
In the lateral region, pain can be caused by the IT band.
The 2 most common conditions that will give you pain in the front of the knee are patellofemoral pain syndrome (PFPS) and patellar tendinopathy. PFPS usually presents as diffuse pain in the front of the knee with activities like squatting, running and going up or down stairs. It is caused by too much load through the patellofemoral joint (knee cap) which can happen because of abnormal anatomy, altered movement of the knee cap in the groove of the knee, muscle tightness (hamstrings and/or quads) or muscle weakness in the hip, knee or foot (which leads to abnormal movement of these joints). Other than abnormal anatomy (of the groove of the knee or the shape of your knee cap), all things that may lead to PFPS are related to how you move (and then how often you move that way).
Of course, it’s easy to understand why abnormal movement at the knee might lead to knee pain. But, why would muscle weakness or abnormal movement of the hip and foot have an impact on the knee? The way I explain this comes down to the function of each of these joints. The hip is a ball and socket joint, it can move in almost any direction. The foot is made of 28 bones and 30 joints, each of these producing a small amount of movement, but which allow the foot to easily adapt to different surfaces and positions. In contrast, the knee’s primary movement is bending and straightening, with a small amount of rotation. When things go wrong in the hip or foot, they have more ability to adapt, but the knee is stuck in the middle with limited adaptability, which means it can often “break down” or present with pain before the hip or foot do.
When dealing with PFPS, what can (not always) happen is poor movement in the hip or foot, which changes the position of the main bone of that joint (femur in the hip, or tibia in the foot), both of these bones come together to make the knee. If you change one of these bones’ position, the knee is in an abnormal position but does not have enough freedom to adapt. Then you go for a run… and load it over and over. These changes in position are not major changes, and may not even be obvious when you’re standing. Sometimes the changes are in how your body moves and only happen to a small degree during motion. Even so, when you do the same thing repeatedly, small changes can make a big difference.
If you read my post about cyclists, you know Dad complained about knee pain on the same side his foot turned out. When he clips his shoes in, it forces his foot forward. One of two things may happen to allow for this to happen… the first would be the tibia turns in and the second would be the femur turns in. Both of these compensations would allow his foot to clip in the right position. However, either of these would change the relationship of the bone at the knee and affect how the knee functions.
Patellar tendinopathy affects the tendon below the knee cap. Tendons connect muscle to bone so that when the muscle contracts, the tendon which is less elastic, pulls on the bone to which it is attached and the bone moves. Tendinopathy is a complex issue that I could write a completely separate post on and probably not cover everything we know (and don’t know) about it. But no matter where the tendinopathy happens (knee, glute, shoulder), the same principles (more or less) will apply.
Tendons are less elastic than muscle but are extremely strong. They are made of collagen that line up in the direction of force (in the patellar tendon, this is up and down) so they can absorb and release force when the muscle contracts and movement happens. When an activity is performed, the tendon gets strained just like other structures and needs time to get stronger. However, they have a lower blood supply than muscles do and blood brings all the good stuff that helps things heal and get stronger. That means in situations when your demand is too high for your capacity or you repeatedly load the tendon without enough recovery, the tendon doesn’t have enough time to get stronger. When it comes to tendons, there is a spectrum of “damage” and depending where you are on the spectrum, what you do about it will be different.
Patellar tendinopathy tends to present as progressive patellar tendon pain. It hurts when you push on it and is painful during activities like going down stairs or jumping. It usually does not just get better with time, and even with the proper rehab plan, tends to progress frustratingly slowly taking months to years in some cases.
The last diagnosis I mentioned with regards to pain in the front of the knee is Hoffa’s fat pad syndrome. There is a chunk of fat that sits between the femur and tibia in the knee filing in space. It is mobile, can change in shape and size during movement of the knee and can help stabilize the knee cap, the patellar tendon and prevent pinching of the joint’s membrane. It presents as pain in a similar area to patellar tendinopathy but is usually associated with some type of event, after which knee pain starts. However, in some cases it can happen with patellar tendinopathy and may be difficult to distinguish from patellar tendinopathy alone.
The main overuse condition that happens on the outside of the knee is iliotibial (IT) band syndrome. It is thought to happen because of repetitive friction of the IT band over the outside of the knee bone when the knee bends and straightens or because of compression of structures below the IT band which get irritated and result in pain. Regardless, the main area where this happens is around 20-30o of knee bending, which is common in both running and cycling. The pain can be sharp or burning but may range in intensity depending on how long it has been developing. It is a condition that can come and go over time depending on activity level but often requires attention to things that trigger the onset of pain.
There are two conditions we can talk about along the inside of the knee. The first is pes anserine bursitis. The pes anserine is an area on the inside of the knee where 3 structures come together to attach. The gracilis (a long slender muscle along the inner thigh), the semitendinosus (one of the hamstring muscles that has a long rope-like tendon) and the sartorius (a thin band-like muscle that overlies and crosses the quads). Bursae exist all over the body, they are like balloons with a small amount of water in them – not enough to fill them up, but enough to allow either surface to glide over the other. Bursae allow structures to slide and glide over the other smoothly, including muscles and bones. With abnormal, repetitive movement, the involved structures can become irritated leading to an increase of the “fluid in the balloon”. This might present as pain, redness and/or swelling in the area. Activities that may be aggravating are running, rising from sitting, going upstairs or sitting with legs crossed.
The second condition is a meniscal tear or irritation. I’m choosing to talk about the meniscus here because the medial meniscus (or the meniscus on the inside of the knee) is most commonly affected. The menisci are pieces of cartilage between the femur and tibia which help absorb shock, distribute force and make the knee fit together better (the tibia is flat and the femur is round, the meniscus is flat against the tibia and bowl shaped for the femur to sit in). When the knee bends, more force goes through the meniscus. Any change in the meniscus will change load distribution across the knee. While the meniscus can tear during an acute injury (twisting of the knee or with an ACL injury), repetitive stress can also lead to irritation of the meniscus. When tears happen in the meniscus happen over time and because of overuse, it is associated with arthritis. That being said, they aren’t necessarily painful (and neither is arthritis). Confused yet? That’s a conversation for a rainy day, and it can get very complicated. For now, just know that having arthritis doesn’t necessarily mean you’re guaranteed pain, but it may mean you do.
The back of the knee is a funny thing. There aren’t any really specific structures that can be pain generating right down the middle of the knee. For example, if you’re stretching your hamstrings and you feel a pull in the back of the knee, you aren’t stretching your hamstring, you’re stretching your sciatic nerve, and that’s called nerve tension. When you feel this, the problem isn’t in the knee, it’s somewhere higher up (back, pelvis, hips or hamstrings). Your hamstrings actually run on either side of the back of the knee, and are pretty tendinous in that region (meaning there isn’t a lot of muscle), so you aren’t likely to feel a whole lot of stretch there. While tendinopathies can happen in any tendon, hamstring tendinopathies aren’t very common. You are more likely to strain or tear the hamstring, and this happens closer to the mid-section of the muscle or near your butt.
What can happen and be felt in the back of the knee, is a Baker’s cyst. A Baker’s cyst is an overproduction of synovial fluid (that little bit of water in the water balloon), which occurs because of irritation of the lining of the joint. It accumulates in the joint capsule (balloon), and as it does, takes up more and more space. Rather than feeling outright pain in the joint, one usually feels pressure, particularly when bending the knee or kneeling. If it’s big enough, you might even feel some “swelling” or see some bulging in the back of the knee. Range of motion might also be limited. Just imagine that water balloon has more water in it, and putting it behind your knee… you won’t be able to bend as far. A Baker’s cyst is associated with conditions that irritate the lining of the joint, like a meniscus tear or arthritis.
SO, WHAT DO I DO?
In this post I talk about a bunch of different conditions in the knee, so of course it doesn’t make sense that there would be one solution for them all. Unless you use an umbrella term which is not specific to any kind of treatment or intervention and would be applied differently depending on the condition. A term like “load management”. Load management, recently made popular by Kawhi Leonard, is what it sounds like. You manage the load (or demand) you put on your body. You allow your muscles, tendons and bones time to recover between activities, giving them time and resources (sleep and proper nutrition) to get stronger. Then you exercise again, only you do a little bit more, and on and on you go, getting stronger. Often times if you do this progressively enough, your body has a chance to make the relevant structures strong enough, even if you aren’t moving well. Depending what your diagnosis is, the load you need to impart may be at the hip, knee or foot. This is where someone who knows what they are doing can help point you in the right direction and give you the appropriate exercises required. Patellar tendinopathy in particular requires specific exercises and loading, and even with a progressive supervised program can take months to improve.
At the end of the day, getting stronger will almost always be the answer to your problems. The manner in which you get there will definitely have an effect as well. But one thing that chiropractors are good at is biomechanics: understanding how your joints function, how your body moves and how that stresses the bones, muscles, tendons and joints. This is an important component contributing to conditions such as PFPS, IT band syndrome or pes anserine bursitis. Abnormal biomechanics can put additional strain on muscles or structures that aren’t 1) used to the additional strain and 2) aren’t meant to be doing those movements. Combining proper biomechanics and a progressive strength program can address a large variety of problems in the knee, as well as most places in the body.
Now, we all like a quick fix, but the sad reality is that these quick fixes are either lies (that pill that will get you thin in a couple weeks) or very short-term options that likely don’t fix the problem (anti-inflammatory creams). There are few times I actually recommend these quick fixes, as I believe it is more important to address the problem leading to the “problem”. But PFPS is a situation where you can see an improvement, IN THE SHORT-TERM, with the use of orthotics. Important to note here is that this is only helpful in the short-term, the biomechanics and strength still need to be addressed in order to have a lasting change. Some practitioners may recommend taping, but the research here doesn’t support its use. Studies show that both actual and placebo taping strategies improved pain!
And here is my friendly reminder that while interesting and informative, this article does not replace a full assessment by a licensed healthcare provider. If you are concerned about your knee pain, I recommend you see someone with the appropriate training to assess and diagnose your pain or injury!
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ABOUT THE AUTHOR
Dr. Melissa Corso has an undergraduate degree in biomedical sciences and a Masters degree in human health and nutritional sciences from the University of Guelph and was a former Varsity soccer player. She graduated from the Canadian Memorial Chiropractic College (CMCC) in 2016 and completed the Sports Science residency in 2018. In 2019 she became a fellow of the Royal College of Chiropractic Sports Sciences (Canada). Dr. Corso is in private practice at an inter-disciplinary clinic in Richmond Hill, Ontario and a research associate at the Centre for Disability Prevention and Rehabilitation at Ontario Tech and CMCC. In her spare time, she enjoys working out, playing soccer and reading.