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Are Deep Squats Bad for your Knees?

June 18 2012

There are lots of articles online about the safety of deep squats, but I don’t think most convey the truth or the uncertainity involved.

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Why deep squats were considered unsafe?

Knee Stability: In 1960, Klein showed that olympic lifters who performed deep squats had an increased incidence of ligament laxity compared to a control group. He also supported his results with a study on cadavers. Based on the in vivo and cadaveric studies, Klein recommended parallel squats than deep squats. His studies led the American Medical Association cautioning against deep squats due to their potential for severe injury.

This led people to believe that deep squats are unsafe.

Why deep squats are considered safe now?


Other Studies: A number of later studies showed that there is no significant knee instability associated with deep squats. Meyers performed a study which had the subjects do deep squats with varying depths. He used the same measurement techniques as Klein and did not find any knee stability issues with deep squats.Chandler did another study comprising of powerlifters, olympic lifters and a control group and concluded that the squat did not have negative effects on knee stability and may be considered safe in terms of not causing permanent stretching of the ligaments. There are other studies to show that there is no excessive movement of the knee that could indicate knee instability due cruciate or collateral ligament damage.

Since the above studies goes against Klein’s conclusion which started the whole ‘deep squats are unsafe’ message, people now believe the exact opposite conlusion- that deep squats are safe.

What is wrong with both the conclusions?


Cartilage and meniscus: The greatest potential for injury with deep squats would be to the menisci and cartilage. But Klein and other studies were looking at knee stability (determined by ligament laxity) instead.

  • Unfortunately, we do not know what magnitude of compressive forces (patellofemoral and tibiofemoral) can be damaging to the menisci and cartilage.
  • Unlike the ligaments, menisci and cartilage do not get stronger and thicker with repetitive loading. They just wear off and cause patellofemoral degeneration and pathologies, such as patella chondromalacia and osteoarthritis.

So we were all focusing and basing our conclusions looking at the wrong tissue.

Compressive Forces: Both patellofemoral and tibiofemoral compressive forces are highest at maximum knee flexion. There is usually a small decrease in patellofemoral forces in higher knee flexion angles due to increase in patella contact area. But this only results a slight decrease in force, and this where the confusion arises.  So the authors would say there was no significant difference in patellofemoral forces at 70 and 110 degrees. This doesn’t mean that the forces are the same.

For example, in this squatting study there was no significant difference in peak patello femoral stress between the three squatting depths (70, 90 & 110 degrees) (P=.35). But if you look at the forces (10.8, 11.7 and 12.3 Mpa) it is clear that they are increasing with deeper knee angles. So at 135-150 degrees (deep squats), the forces will be at the highest. The forces are increasing and if they used enough sample size, they will find it statistically significant too.

Since the forces are high, there is greater risk of damage to the cartilage and menisci with deep squats. So we cannot conclude that deep squats are safe.

Ideal study: The ideal study to test if deep squats are bad for knees is not an 8 week study or a study which looks at compressive or shears forces as we have seen. What we need is a study where a large group of people who deep squat and another group of people who does parallel squat are followed for 15-20 years. If deep squats are bad for the knees, you will see more people with knee pain in the deep squat group.

The problem with picking a bunch of olympic lifters and testing their knees for damage and pain is that the people who already had knee pain or other problems might have stopped squatting or switched to paralleled squatting. The people who are already deep squatting might be the ones who were blessed with some good knees or have better squatting biomechanics and so forth

Unless we have study like the above, we can never conclude anything about deep squats and safety with certainty. Just like in most cases, we are just simply leaning towards a side based on our personal experiences and observations and just confidently concluding.

Science and anecdotes: Usually in these type of articles, pictures of lifters (look above) doing ass to the ground squats with heavy weights is added just to seal their argument of why deep squats are safe. As I wrote, this doesn’t add anything to a scientific discussion. People who write scientific articles shouldn’t mix their personal experiences or observations or results. That is defeating the whole purpose of using scientific studies. It makes as little sense as one of those swiss balls that comes with a stand for people to sit on. If you are unaware, a bosu ball is used to create an unstable environment. But by using a stand underneath the ball and hence making it stable, you are just defeating the whole purpose of using a bosu ball. 

Practical Applications

  • We know the patelleofemoral and tibiofemoral forces are at the highest during deep squats. What is uncertain is if these forces will actually cause cartilage/menisci damage and end up showing as knee pain. This will depend on a lot of other factors such as genetics, the weight you use, how often you squat, age and so forth.
  • Considering how pain is extremely complex and is not linearly related to damage, the issue becomes all the more complex.
  • If you are an olympic lifter, you have no choice but to deep squat. If you are a bodybuilder, it might be better to deep squat to target your glutes. If you are a lay person who wants to look good and love having some heavy weight on your shoulders, there is no compelling reason for you to do deep squats. If you are a 50 year old with some nagging knee pains, it may be better to avoid deep squats
  • To sum it up, there is no conclusive evidence to show deep squats are either safe or unsafe for your knees.
  • Contrary to what most people think, research will rarely give a definite yes or no answer that we all love;there is always some uncertainty. Our job as evidence-based practioners, instead of ignoring or disregarding the uncertainty, is to accept the uncertainty and convey it truthfully.

 
Reference 1
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Karky | Tue June 19, 2012  

Nice article. Do you know if there has been done any research on squatting depth and the patella tendon. You often hear the argument that with quarter squats you use your quads more and your glutes less and thus more force transfer will occur over the patella tendon. However, I’ve never really seen anyone look into this scientifically.

Anoop | Tue June 19, 2012  

Thanks Karky!

As the depth increases, there is greater glute activity. Part of the reason you feel more in quads is in quarter squats people are using a lot more weight than parallel or deep squats. And in quarter there is greater forward knee movement beyond your toes than parallel squat.

Brad Schoenfeld, MSc, CSCS | Tue June 19, 2012  

Good summation, Anoop. As you correctly point out, the evidence simply isn’t there to support the claim that deep squats are bad for the knees. And there is a lot of implied evidence that leads us to believe it should not have a detrimental affect on the ligaments. But current research is limited and we certainly need long-term longitudinal studies to better assess the topic.

As always, you provide a well-balanced, objective analysis of the data. Great work!

Brad

Omar | Tue June 19, 2012  

Great article Anoop! Your training articles are my favourites. How do you squat, parallel or deep?

Patrick Wenning | Tue June 19, 2012  

I agree with the knee movement beyond the toes. Why doesn’t anyone look at where the center of gravity is during the squat and how that effects the pressures in the knee, or the ratio of ankle to knee to hip flexion during the squat. Doesn’t it always come back to posture?

Quagwire | Tue June 19, 2012  

Very nice article.  I would just like to mention that osteoarthritis is much more complicated than a “wearing down of cartilage”.  I often see it broken down this way online, where in real life it is a complex inflammatory condition with cartilage breakdown.  Many people have perfectly healthy cartilage after many many years of joint friction.

Anoop | Wed June 20, 2012  

Hi Brad,

Thanks a lot! Your recent NSCA articles was one of the references. I think we are lucky to have people like you who can write what we know and what we don’t know without stuffing in your personal observations and results like every single article out there. So thank you.

Hi Omar,

Thanks again bro. I go deep, but I have my beliefs,goals, biomechanics and preferences that might be completely different than you.

Just so that you know that’s good enough reason not to take my recommendations about deep squats:-). Just too much confirmation bias you know. I only wrote about it because you asked.

Hi Patrick,

Thanks! When studies do squats, they are aware of the proper form than most of us and they are using subjects who are experienced not novices.

Hi Quagwire,

Thanks!I would agree. I haven’t really looked into the condition itself. And many people have no cartilage and no pain. That is the mystery of pain.

Karky | Thu June 21, 2012  

But what does this greater quad usage in shallow squats do with the patella tendon? Just an anecdotal observation, but I know lots of people who squat like their body is on top of their legs (if you know what I mean) instead of dropping down between their legs like in a deep squat, and pretty much all of them have “jumpers knee”. So I was wondering if there is any scientific data on what kind of squat is more dangerous for the patella tendon, as it would seem to me that this is a common place for injury in squatters.

Anoop | Thu June 21, 2012  

Hi Karky,

Haven’t come across any study looking at squats and jumpers knee.  Athletes who are doing a lot are usually candidates for these. The forces on the patellar tendon is greater as you go deeper and with greater anterior knee translation. So it is a possibility if you do a lot of squats with that form.

Kelly | Fri June 22, 2012  

Hi Anoop,

Great science based article like always, keep up the great work. See you soon

Anoop | Sun June 24, 2012  

Hi Kelly.

Thanks for the comment.

Jonny | Sun July 08, 2012  

Hello Anoop,

Still on the subject of knees, do you have an opinion on the safety of seated leg extensions?  I used to love doing this exercise as it seemed to be the most effective at developing the quadriceps.  But then somewhere I read an article written by a knee surgeon stating that seated leg extensions were very bad for the knees, so I have backed off on doing these.  Do you have an opinion on this?

Thanks Anoop.  You have a great website here!

Rex | Wed August 01, 2012  

What do I think?

I think that this article clearly points out why people should be just as skeptical of “science” as empirical observations or anecdotes.

Anyone with a single functioning brain synapse knows that the best position from which to perform squats, or any exercise, is the one that is biomechanically natural.

To belabor the obvious, we should perform squats in the same position that we use to defecate in the woods—yes, an ATG squat. It’s the position out of which we have the most power to rise. When has anyone ever squatted to “parallel” in their daily lives?.  Stopping at “parallel” puts all of the pressure on the knees. 

The only “science” I’m interested in is that which is conducted by an Olympic gold medalist who earned multiple PhDs from a Tier 1 university and paid for the study with his or her own money.  Cynical?  Uh, of course.

Anoop | Thu August 02, 2012  

Hi Jonny,

I haven’t looked into recently. But when someone says stuff like very bad and such, then they need some solid proof. Since he is knee surgeon he is only seeing people with a lot of knee pain and not people who have no pain. So keep that in mind.

Hi Rex,

This is called system 1 thinking. Jumping to conclusions because it just seems right.

Have you ever deadlifted? I pick up a penciil with a rounded back (and so you and everyone). Do you deadlift with a rounded back too since that is the most natural position? Think about it.

Karky | Thu August 02, 2012  

While I’m not taking any sides between Anoop and Rex here, I’d just like to point out that I think the most natural way to pick up a pencil is an ATG squat.. at least that is how children do it wink

Anoop | Thu August 02, 2012  

H Karky,

What a kid does is totally different from what we do as an adult.

What is most natural for a kid is because of the biomechanical factors that is inherent at that age (like low center of gravity, mobile joints and tissues and so forth). This is not what happens as you grow up. And if indeed we had to stop and think this is how a kid picks it up and let’s do it this way, then it is no more natural you know.

We had a thread in the forum about little kid doing a squat and how everyone posts it on facebook everyday to show how a squat should be done.

And I now you know this very well and you are just throwing out a different angle to the discussion.

Karky | Fri August 03, 2012  

Yeah. I guess it’s really a question of how you define “natural”. Is it the way a baby does it, or is it or do you count in the constraints that comes with growing up, such as losing your mobility.
and about the baby picture, the baby does have good form and I don’t see any problem with an adult striving to get to that point by improving their mobility, etc.

Rex | Fri August 03, 2012  

You’re right, Anoop, it is System 1 thinking, because squatting is one of the seven primal movements, not unlike bending, whether to deadlift 610 lbs. (as I do) or picking up a pencil. 

We pick up a pencil with a rounded back because it, too, is the most natural.  Likewise, we pick up extremely heavy objects (> 90% of 1RM) with a rounded back because it is the only way we can generate enough strength. 

I’m in favor of System 2 thinking when unfamiliarity demands it, but too often it is used by pseudo-intellectuals to complicate the uncomplicated.  This is why science so often postdates broscience or, more delicately, empirical observation, by a decade or more in many cases.  In the meantime, the broscientists are 210 lbs. and 6% body fat, and the System 2 thinkers are still wondering if squatting ATG might hurt their knees.

Man up and lift the weight.

Adam | Wed August 29, 2012  

Hi Anoop, I’ve just came across this site and have been impressed with it’s quality, thanks for the posts.

I’m glad you’ve brought up the squatting debate because it gives me a chance to ask a question that’s always bugged me whenever this issue comes up.

In large parts of the world deep squatting is still a regular part of everyday life, if only because a large number toilets are still of the squat variety, has anyone ever made a study of these populations and their knees? I understand there are lots of other factors that could effect the results of a study of this kind, but it’s always seemed silly to me that research is carried out in populations where squatting is not a common movement.

Anoop | Fri August 31, 2012  

Hi Adam,

Thank you and welcome.

Even if squatting is regular pattern, adding weight on top of the body weight would make a difference.

And if the applicability is for non-squatting nations, the research better be with subjects from non-squatting countries right?

This is just one topic that is classic example of confirmation bias. People who deep squat will find evidence for deep squat and people who parallel squat would find evidence for that. Another reason why we should look at research.

Adam | Mon September 03, 2012  

Thanks for your reply Anoop and that deos make sense.

It makes me realise I’m bringing my own bias to this, I’ve always been made aware of this argument in relation to squatting in general (I’ve had people refer to both papers to justify the practising/not practising of normal un-weighted squatting in practising like yoga) so when I read this article I naturally lent to interpreting it that way.

Re-reading I realise you and your commentators are speaking more of Olympic lift style weighted squatting which, as you point out, is a totally different ball game. 

So would a more accurate title be ‘Is weighted squatting in countries where squatting is not an everyday activity dangerous’?

Doug | Wed October 10, 2012  

A couple of other factors to consider on the relative health of deep squats:

1. Joint mobility - inflexible ankles leads to the knees and hips picking up the slack. Same goes for bunged up hips…the knees are stuck picking up the slack for the hips & ankles

2. Squat technique - a hip dominant squat style (picture a Westside box squat) changes the amount of knee flexion significantly. Olympic & bodybuilding style squats are more knee dominant

Anatoly | Thu April 18, 2013  

Hi, Anoop
For someone who want to limit the squat depth what will be a preferable option? Box squat?

Dwayne Wimmer | Mon April 22, 2013  

Well done.  I will be sharing this with my staff and others!!

Dwayne Wimmer
Owner
Vertex Fitness Personal Training Studio

Wyatt | Tue October 22, 2013  

So which is a learned movement: To squat ATG like a child or to round our backs to pick up a pencil? Does our joint mobility and flexibility diminish with age because at some point we stop using it? Are these factors considered when any of these “studies” are conducted, or do we operate on the assumption that we are how we are because that’s the way it is… i.e. is there a better way, and what are we doing to learn/promote it?

SNRGYathletics | Sat March 29, 2014  

Hi Anoop, you wouldn’t have to pick up a pencil with a rounded back if you just squatted down deep enough to grab it with your back straight. Also, you’re right about biomechanically defaulting to a rounded back. If you watch a strongman competition, you’ll find that deadlifting (an odd object) with a rounded back is the go to form. As a fact, Kelly Starett (world renowned physio working in the crossfit community) teaches in his book “becoming a supple leopard” that you can have your back rounded as long as you know how to create intra-abdominal pressure to brace your spine. Primitively, it would have been the only position we could lift odd, heavy objects with. Great website by the way!

madi | Sun June 15, 2014  

I’m going to tell you right now deep squats ARE bad. I have no clue how this whole deep squat thing snowballed but apparently it’s from crossfit. i am the daughter of a professional football player and had this conversation with my dad. He explained that when he played, he had professional trainers tell him that squatting that low is dangerous and you could easily blow out your knees. You don’t have to take my word for it, but i’m sure you’d be much more inclined to listen to a professional athlete instead of some gym goer. Again, don’t know how the whole deep squat thing started but please, please, please don’t squat that low!!

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