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.
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.
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.
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.
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