Episode #31: Functional Anatomy of the Knee in Barbell Training With Dr. John Petrizzo, PT, CSCS, PRSCC, SSC
Understanding the functional anatomy of the knee in barbell training is an important aspect of biomechanics that powerlifters, physical therapists, chiropractors, strength coaches, and doctors should understand.
When you understand how the knee joint is structured and functions you’ll have a better understanding of why certain ways of performing the squat and deadlift are more optimal than others. This will also help you understand the normal forces on the knee joint and how we can combine our knowledge of powerlifting programming and barbell movement mechanics to maintain healthy, pain free movements despite atypical structure and joint degeneration.
“All of this is normal in the human body. This is just the anatomical structure that we have. So we don't want you to hear this word "stress" or the fact that we're talking about this anatomical structure of the human body and think, "oh, shit, that's bad."
In this episode of the PRS Podcast, PRS Clinical Coaches, Drs. Rori Alter, Alyssa Haveson, and John Petrizzo discuss the role of the knee joint and its surrounding structures in the mechanics of barbell training.
This episode is an educational experience for barbell trainees, powerlifters, Crossfitters, weightlifters, and other strength lifters to deep dive into the knee joint.
If you’re a chiropractor, physical therapist, medical doctor, strength coach, or student clinician, this episode is a great review and application tutorial regarding the knee and barbell training.
In this episode we discuss the:
Joints that make up the knee
Normal movement of the knee joint
Internal structures and surfaces of the knee
Musculature responsible for knee flexion and extension
How the hip affects the knee
Patellofemoral movement
ITB pain
Resources mentioned in this episode:
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Dr. Rori Alter, PT, PRSCC, SSC: [00:00:04] All right. Welcome back to the Progressive Rehab & Strength podcast. I'm your host Dr. Rori Alter here with my lovely co host, Dr. Alyssa Haveson, a clinical coach here at Progressive Rehab & Strength. And we've brought on another clinical coach here at Progressive Rehab & Strength who you've heard on the podcast before, if you've been around a little while. Dr. John Petrizzo He is not only a physical therapist and barbell strength and powerlifting coach, but he is also a professor at Adelphi University in the Exercise Science department, and we're bringing him on today to have a discussion all about the biomechanics of the knee joint in barbell training. So the purpose of this episode is to bring more knowledge to lifters about the structures involved in or around or part of the knee joint, how the knee joint actually moves in normal human movement, connect that to barbell training and then talk about how this stuff might be influenced by pain and injury or might influence pain and injury. But before we dive into understanding that, we do want to remind you that pain in a particular area of the body or with a particular movement in barbell training is not only or always related to a structural issue in the area that you're experiencing pain. So we have three full episodes discussing pain and injuries and barbell training. So we'll link those in the show notes for you guys. But the Pain and Injury series is a really good place to start if you're experiencing any pain in your knee and barbell training. So John, tell us a little bit about the knee and the structure of the knee joint and how it moves in space, both from a joint perspective and a larger perspective within the kinetic chain.
Dr. John Petrizzo, PT, PRSCC, CSCS, SSC: [00:02:08] Okay, sure. So the knee is really comprised of two separate joints. So we have the patella femoral joint, which is essentially the interaction between your kneecap and your femur. And then we have the tibial femoral joint, which is the interaction between the tibia and the femur. And those two joints really have three distinct compartments. So the tibial femoral joint has a medial compartment and a lateral compartment. And then there's the patella femoral compartment. So together, those joints basically functioned simultaneously to produce the different movements that we get at the knee. And the knee is a relatively simple joint in terms of movement. So it primarily just flexes and extends. We would say that it has one degree of freedom. So the number of degrees of freedom a joint has indicates the number of different planes that it moves in. So we have three different planes of motion. You have your frontal plane, your sagittal plane, and then your transverse or horizontal plane. So the knee primarily is going to work in the sagittal plane when we flex an extended. So it has one degree of freedom. So it's pretty simple from from that standpoint where it gets a little bit more complex. Is that there there is some rotational movement that occurs at the knee joint as it flexes and extends. The reason that we don't consider that. All that much when we're talking about its function from a mechanical perspective is because we don't have any voluntary control over that.
Dr. John Petrizzo, PT, PRSCC, CSCS, SSC: [00:03:54] So that's really the result of the anatomy. So the femur. Is slightly twisted. It has a torsion angle in it. All right. So if we're looking at it from from the hip, we call the angle of torsion, which is where the femoral head and neck sit relative to the condyles, which are down at the bottom of the femur. And then the tibia also has a little twist in it or torsion angle. In addition to the fact. So those two compartments that we talked about, the medial and lateral compartments aren't equal in size with each other. So the medial compartment is much larger than the lateral compartment of the femur, so of the knee. So the medial femoral condyle is larger than the lateral condyle. The medial tibial plateau is larger than the lateral. So because of these essentially twists or slight rotations that we have in the femur and the tibia and the difference in the size of the medial and lateral compartment of the knee, as we flex and extend, there is going to be some rotational movement of the knee, but it's not something that we voluntarily control. We voluntarily control the flexion and extension that occurs. So hopefully that makes that makes sense.
Dr. Rori Alter, PT, PRSCC, SSC: [00:05:18] I have a question. So, I don't know the statistics on this from a research perspective, but in my clinical experience, there's more medial meniscus tears than lateral meniscus tears. Would you say that's kind of?
Dr. John Petrizzo, PT, PRSCC, CSCS, SSC: [00:05:39] Oh, yeah. So. So we wait bare more through the medial compartment versus the lateral. So there's the higher incidence of medial meniscus injuries versus lateral. There's a higher incidence of MCL injuries versus LCL injuries. There's also a higher incidence of osteoarthritis in the medial compartment as opposed to the lateral compartment. So, the medial compartment is larger, but we do put more compressive force through the medial compartment, and that is most likely the reason why we see higher incidence of pathology in that part of the knee.
Dr. Rori Alter, PT, PRSCC, SSC: [00:06:18] Would you also say that because it's larger, there's more motion that's occurring in the medial compartment and that might also be contributing to it?
Dr. John Petrizzo, PT, PRSCC, CSCS, SSC: [00:06:29] Well. So if we're talking about if we're talking about stress on the medial side of the knee, then we have to talk about valgus and varus stress. So valgus stress is a is a type of stress that is applied from a lateral to medial direction versus varus, which is the opposite. So it's a medial to laterally directed force.
Dr. Rori Alter, PT, PRSCC, SSC: [00:06:51] John, for people who don't know the terms or understand the anatomy and the term medial to lateral, like what does that look like, that's from outside to inside and inside to outside of the knee, correct?
Dr. John Petrizzo, PT, PRSCC, CSCS, SSC: [00:07:05] Right. So from lateral to medial, it would be from outside to inside and then vice versa for varus stress. So medial to lateral be from inside to outside. So at the knee joint, we tend to have more valgus stress as opposed to verus stress. So we tend to have more stress applied in that direction. And that has to do with the interaction between the hip and the knee and to a certain extent, the foot and ankle as well. So the knee joint. The way I look at it, it's it works together with the hip and the ankle, and it's in between those two different joints, right. So various different issues that can come up in regards to the hip and the ankle can have an impact on the knee joint. But so, for example, one of the things that we look at is called the Q angle or quadriceps angle, and that's essentially the difference between the lateral part of the hip and the center and center of the knee and the resulting difference between those two points. For most people, it's going to be somewhere between ten and 20 degrees on average. But that is a contributing factor to why we have more valgus stress at the knee joint because our hips are a little bit wider right than our than our knees are something at the ankles. So like pesplantus or having an overly promoted foot and ankle in a resting position where you have a decreased arch. Right. So you can say you have flat feet that can contribute to a little bit more value stress at the knee as well. So there are all these little things that can that can contribute. But for just about everybody, you're going to have some sort of difference between the hip and the knee joint in terms of that Q angle, and that contributes to having a little bit more stress at the knee, which then applies more stress to the medial part of the joint.
Dr. Rori Alter, PT, PRSCC, SSC: [00:09:02] And just to clarify, for people who are concerned about the term stress, all of this is like normal in the human body. So this is just the anatomical structure that we have and it's designed this way for our muscles and our body to move in space well. So the Q angle, like, you don't have to get so obsessed with the Q angle and flat feet and varus and valgus stress and all that stuff, because this is these are the this is the normal position and everybody's going to have their normal whatever they were born with. So like I have flat feet, we can also talk about genu recurvatum, but I have like hyperextended knees, I have valgus at my knees. My knees don't hurt, so we don't want you to to hear this word stress or the fact that we're talking about this anatomical structure of the human body and think that, oh, shit, that's bad. This is just normal. But this is why people tend to get more symptoms or injuries on the medial side of the knee versus the lateral side of the knee. Does that make sense now?