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Is knee valgus actually a GOOD thing? New research

Categories: Videos & podcasts

Chapters:

00:00 Introduction

00:30 How knee valgus affects the biomechanics of squatting

01:59 The resulting adaptations

03:30 Can you fix knee valgus?

04:28 How safe is knee valgus?

05:45 Conclusion

Transcript:

When you’re squatting, you may experience that your knees cave in, especially during the upward phase of the movement as you come out of the hole. This is called knee valgus. Knee valgus looks kind of ugly and is generally considered poor technique, something you should fix, in particular by strengthening your glutes because your adductors are too strong or too tight they are pulling in your knees. Your glutes are too weak and not capable of pushing your knees out. All of this might very well be wrong.

A new study investigated how knee valgus, or the opposite – pushing the knees way out, affects the biomechanics of squatting. They looked at people that could squat two parallel and could squat at least 1 to 1.5 times body weight. 1.5 times for men. So he basically looked at people squatting with either knee valgus, the knees coming in, pushing the knees way out, or squatting normally with their regular technique. And then they looked at what are the demands on the particular muscles during the squat. The key finding was that knee valgus, the knees caving in, reduced the demands on the hip adductors that pull the knees in and it increased the demands on the glutes. The abductors that get to push the knees out. Now this can happen due to a change in the lengths of the muscles and due to leverages that these muscles have. During a squat you want hip extension which essentially pulls you up out of the squat. It’s like the good morning portion of what you’re doing. That is done by the adductor Magnus and the gluteus maximus primarily. So the hamstrings are basically inactive because they have a bi-articular muscle conflict. Hamstrings are essentially not trained by squats because if the hamstrings were contracting, they would also pull you into knee flexion, which kind of pulls you back down into the squat. So whereas they would like to help at the hip, they cannot because they would be sabotaging the quads at the knee. And a muscle can only contract or not contract. So the hamstrings are essentially just the stabilizers during a squat. So it’s basically the adductor magnus and the abductors, the gluteus maximus that propel you upwards during a squat that do the active hip extension.

What knee valgus does is it shifts the demands, or in general the positioning of your knees these two muscles. And that can be biomechanical advantageous when a muscle is just a little bit too weak or cannot produce enough force to get through the movement at that portion. By shifting the knee position, body essentially redistributes the load and the forces to make you capable of squatting more weight. In particular, what knee valgus seems to do is it shifts the loads and the demands to the glutes in the portion when you are coming out of the hole. In that sense knee valgus can actually be functional and advantageous. And ironically, the standard advice to strengthen your glutes may thus work adversely because what knee valgus does is it shifts the demands from the adductor magnus to the glutes. So if you have stronger glutes, the body might be extra incentivized to make you go into knee valgus to load the glutes more. So the standard advice to strengthen the glutes and to stretch your adductors, that definitely doesn’t work, but strengthening the glutes in particular might actually make things worse.

And that might actually also explain why we see so much knee valgus, because most people, they’re training the hell out of their glutes, athletic weightlifters, power lifters, most women in the gym… Even men they train their glutes a whole lot more than their adductors. Most people don’t really train their adductors. The adductor magnus will be trained with your hip extension movements, but it is only a byproduct of the hip extension training that you’re doing, whereas most people are doing very active glute work in a lot of different ways. So I think it’s fair to say that if anything, that most people have an overdeveloped ratio of glutes to adductor magnus. And in that sense, we also know that all of these things that are purported to fix this, they don’t actually work. Like if strengthening the glutes was the solution, if it was a case of muscular imbalance or anything like that, then you wouldn’t see it all the time in the top weightlifters, in the top power lifters, in many athletes… Elite athletes of all kinds display significant knee values. And it’s particularly the case when you’re doing maximal force movements, which also shows that it’s probably biomechanically advantageous. If elite athletes are doing it, and you cannot train it away, like the body is almost forcing you do it, that is usually an indication that is the biomechanically optimal way to perform the movement. Because if you’re telling the body I need to squat this weight no matter what, then the body will make you move in such a way as to produce the highest amounts of forces. So in that sense, this research actually strongly suggests, and I think anecdote as well strongly suggest that knee valgus is a rather natural and probably biomechanically advantageous phenomenon. Now, you might be wondering, even if it is advantageous for force output, isn’t it bad for the knees? It’s great and all that you can maybe lift more weight, but if it messes up your knees in the process, of course you still don’t want to do it, and you want to fix it and it is really a problem. So how safe is knee valgus actually?

The researchers conclude the following: “Although knee abduction moments may strain the anterior cruciate ligament, the ACL, this strain plateaus at a level insufficient to injure the ligaments.” Later on they conclude that “The amount of hip medial rotation in all 3 squat variations may be normal and not sufficient to cause lateral patellar misalignment.” Research in general regarding the safety of knee values during squatting, during drop jumping, during athletic movements is very inconclusive. For example we have one very large study in particular that I think is notable because it was done in elite female athletes and the title essentially sums up the research: “Kiss goodbye to the kissing knees” “No association between a frontal plane inwards knee motion and risk of future non-contact ACL injury in elite female athletes.” research generally at this point is very ambiguous and does not clearly show an effect of knee valgus, whereas it does show that it’s probably biochemically advantageous for certain people to shift the demands from the adductors to the glutes during a portion of the squats when this is beneficial to squat more weight or do more reps. To conclude, what does this all mean in practice?

Well, my take is that you should be able to squat and I teach all my students that they can squat to parallel without knee valgus, especially if it’s a none 1RM attempt. I think you should have the motor control to adequately push your knees out and I think most people, when they are squatting, they are not pushing their knees out enough. They think of the squat as like kind of falling into a harmonica and that’s not how you squat. Squatting is a lot more about sitting in between your knees. Most people can achieve far greater range of motion that way, with more neutral limbal pelvic alignment. That said, when you have the motor control necessary to perform perfect squats in textbook form and you still experience that you’re getting knee valgus during heavy attempts, especially during maximal lifting and it happens almost involuntarily, like you just cannot help it and it also helps you lift more weight, which is usually kind of the same thing, like your body is making you move this way no matter how you try to move, because it’s simply the biomechanically optimal way for your body to perform the movement. If that is the case, you have the motor control not to do it, at least during sub-maximal movements and it doesn’t cause you any pain or discomfort, then the knee valgus that you are experiencing is probably actually functional. It is essentially a good thing, not “a problem” that needs to be fixed. It may look somewhat ugly, but it is probably not really a problem.

There is no strong evidence that it is unsafe for the knees and there is some evidence that it might help you lift more weight. So in that sense I think knee valgus is actually a very functional natural thing. As I explained in my previous video, good exercise technique doesn’t have to look pretty, good exercise technique is simply the movement that allows you to stimulate the desired training adaptations, and in this case knee valgus can definitely be a part of that. So don’t obsess over your knee valgus.


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About the author

Menno Henselmans

Formerly a business consultant, I've traded my company car to follow my passion in strength training. I'm now an online physique coach, scientist and international public speaker with the mission to help serious trainees master their physique.

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