Are Squats Damaging Your Knees? A Myth Explained.

This was supposed to be an instructional post about how to do the kettlebell swing.

Then I got into a conversation with someone. Let's call him Stephen, so that you don't find out that his real name was Jason.

Stephen asked me the best way to lose weight around his mid section, "my spare tire" as he put it.

I explained to him firstly that you cannot target fat loss in that area by doing the sit ups, or for that matter, target fat loss in any way through exercise (I outlined this fact of life in a previous post).

Furthermore I went onto explain that the exercise that uses the largest and most powerful muscles in the body was the squat, and that doing squats would get him quicker results in his midsection than an equivalent amount of sit ups. 

He asked me to demonstrate what I meant by a squat. So I performed a full bodyweight squat, like so.

Pictured: Not what I look like on a Thursday evening.

The conversation then proceeded like so.

Him: "But my basketball coach says that you shouldn't let your knee go further forward than your toes when squatting..."

Further adding:

"...everyone knows that squatting so deeply is bad for your knees"

He then went onto demonstrate his recommended alternative, a half squat (like the above image but only half way down instead of the top of the legs being parallel with the ground.)

Me: "I'm sure your basketball coach is very good, but on this subject he is incorrect"

Cue one overly long debate that culminated in the following:

Him: "So you are right and the whole world is wrong, yes?" (poorly disguised sarcasm)


Did you just say that? The whole world? Really?... As in everybody?!

Kettlebell swings will have to wait.

Deep breath... beginning rant in 3...2...1... 

Firstly, any strength and conditioning coach worth his salt will tell you that full squats with proper technique do not harm the knee. Quite the contrary in fact. Full squats strengthen the ligaments around the knee, subject the joint to even forces from both anterior and posterior directions, and develop the muscles of the whole leg evenly. What this means is that that muscular imbalances are not created as one trains.

Secondly, the whole thing about not allowing your knees to go forward of your toes is totally irellevant. Some people when squatting correctly through their heels, will have their knees pass over their toes, some will not. That's more to do with how long a persons legs are than actual technique.

In many far flung places such as South East Asia, squatting deeply is done frequently and often (eating dinner for example), children deep squat from a young age, and you sit down and stand up from chairs on a regular basis. In essence, squatting is a very natural movement that our bodies are built and able to do.

Furthermore, research indicates that weighted squats in combination with plyometric training is about three times as effective as either squatting with weights by itself, or plyometrics by itself, on improving an athletes vertical jump. This is obviously something very important when it comes to sports like basketball.

The Squat Plyometric group achieved a statistically greater improvement (p < 0.0001) than the Squat or Plyometric groups alone. Examination of the mean scores shows that the Squat group increased 3.30 centimeters in vertical jump, the Plyometric group increased 3.81 centimeters and the Squat Plyometric group increased 10.67 centimeters. The results indicate that both Squat and Plyometric training are necessary for improving hip and thigh power production as measured by vertical jumping ability.

Source: Adams K. et al. (1992). The Effect of Six Weeks of Squat, Plyometric and Squat-Plyometric Training on Power Production. Journal of Applied Sports Science Research. 6 (1), 36-41. 

It is reasonable to assume from the above study, that removing the squat out of a basket ball player's training regime will severely hamper his on court abilities.


But Nick, what about the half squat? I heard that you should do that!

The proponents of the "I read somewhere that deep squats are bad for you" camp don't believe what I just told you. Instead they recommend a "half squat". This is like a true squat but with only around 50% of the range. Your legs don't get even close to parallel with the ground.

The problem with half squats is that they are heavily focused on the quadricep muscle group (front of thigh), they don't fully engage the hamstrings (back of thigh), and have a negligible effect on the glutes (bum). What this means is that you are training the front of your legs, but not the back.

If you're training one side of the body and not the other in any body part, then you are going to create asymmetries in your muscle and ligament structure, this leads to all sorts of problems if such an exercise is made a regular part of your training program.

To add further weight to this argument, the aformentioned Adams K. et al (1992) study used full squats, not half squats.

All That being said, if you have bad squat technique then yes, you certainly can hurt your knees if you deep squat (or half squat for that matter). Here are some guidelines for good squat technique.


The bare bones of squat technique:

  • Have your feet pointing outwards at around 30 degrees to the left and right slightly greater than shoulder width apart.
  • When squatting, make sure that the knees follow the same way the toes are pointing. Not doing this leads to twisting of the knee joint and potential injury of its ligaments.
  • Press your weight through your heels not your toes and make sure your forefoot and heal both maintain contact with the floor. 
  • Squat down low enough so that the tops of your thighs are at least parallel with the ground below.
  • Keep looking forward and slightly upwards through the movement, not down at your feet. They already know what to do without you watching them :-)


Where did the myth that deep squats are bad for you come from?

From what I can tell this idea came from a single study done back in 1961 by Klein, K.

Klein said (utilising a self made measuring device) that weight lifters that did full squats on a regular basis were looser in three of the four major knee ligaments. These were the medial and lateral collateral ligaments as well as the anterior cruciate ligament (see below).

Lose ligaments around the knee = less knee stability = greater likelihood of serious injury. The American Medical Association shortly thereafter came out with guidelines advising against deep squatting.

Unfortunately this study had numerous issues with its methodology. The principal element of which was the subjective nature of the testing. Klein would need to physically apply pressure to the instrument with his hands in order to take a reading.

Source: Klein, K. (1961). The deep squat exercise as utilized in weight training for athletes and its effects on the ligaments of the knee. American Journal Physical Medicine and Rehabilitation, 15(1), 6-11

This means that the result of any test would be influenced by the amount of force he exerted. (I mean, could he realistically apply exactly the same amount of pressure for all 488 participants of the study?)

Furthermore Klein asked the participants if they did "deep squats" BEFORE the test was made. Could this have created a bias in the experiment?

What I'm saying here is that this study, that the American Medical Association and many well meaning coaches base their "don't squat too deep" advice on, is pretty sketchy.

What do other studies say?


To put it bluntly... later studies just do not support these findings.

Below I have outlined three studies to show that deep squats, (where you go low enough that the tops of your legs are at or below parallel with the floor) actually strength your knee joints and prevent injury.


Study 1 - Knee ligament laxity in Runners, Basketball Players and Squatting Powerlifters 

A 1986 study in the Journal of American Sports Medicine looked at knee ligament laxity (I.e. ligament looseness) in recreational endurance runners, basketball players and squatting powerlifters. The study found that...

basketball players and distance runners experienced a transient increase in anterior and posterior laxity during exercise, whereas the Squat powerlifters did not demonstrate a significant change in laxity

They went on to conclude...

repetitive physiologic stresses as a high strain rate produce significant ligamentous laxity, while a relatively few large stresses a low strain rate do not

Source: Steiner M, Grana W, Chilag K, Schelberg-Karnes E. (1986). The effect of exercise on anterior-posterior knee laxity. American Journal of Sports Medicine. 14(1); Pp 24-29.

So it seems that ligament laxity is provoked to a greater extent by repetitive running type movments, not squats. Another study in the British Journal of Sports Medicine added further weight to this argument.


Study 2 - Knee Stability from Squats in Powerlifters and College Students.

A 1989 study in the Journal of Medicine and Science in Sports and Exercise looked directly at the squat as an exercise in both the short term and the long term with regard to knee ligament stregnth.

One hundred male and female college students were measured using a knee ligament arthrometer on nine tests of knee stability. Over an 8-wk training program, full or half squats did not consistently affect knee stability compared to non-squatting controls.

To measure the effect of long-term squat training 27 male powerlifters (14 Elite or Master Class) and 28 male weightlifters (8 Elite or Master Class) were measured on the same tests...

... Both powerlifters and weightlifters were significantly tighter [in terms of knee stability] than controls on the quadriceps active drawer at 90 degrees of knee flexion...

No effect of squat training on knee stability was demonstrated in any of the groups tested.

Source: Chandler T, Wilson G, Stone M. (1989), The effect of the squat exercise on knee stability. Medicine and Science in Sports and Exercise. 21(3). Pp 299-303.

So according to this study, squats seemed to have no short term effect on knee stability for the eight weeks. However the power lifters who had been doing squats for years, were tighter in the knee joint than the control group (implying greater knee stability). Which would suggest that weighted squats actually strength knee ligaments in the long term.


Study 3 - Knee stability from squats in American Football players.

our final study is from the 1994 American Journal of Sports Medicine and looked at a group of thirty two American Football players who paricipated in a 21 week squat training program. The participant's knee ligaments were tested at 12 and 21 weeks. The study concluded the following:

For all subjects, no significant differences were found between pre- and postexercise results for active and passive tests. Of the 2440 measurements taken, only 8 demonstrated increased excursions greater than 2 mm.

This study demonstrates no significant increases in anterior-posterior tibiofemoral translation in athletes using the squat exercise as part of their off-season training program.

Source: Panariello, R., Backus, S., Parker, J. (1994). The effect of the squat exercise on anterior-posterior knee translation in professional football players. American Journal of Sports Medicine, 22(6), 768-773.

And so there you have it. The same result yet again. Another study showing squats have no detrimental effect on knee stregnth.


So what conclusions can we draw from this?

The original study into the effect of squats on knee laxity by Klein, K. (1961) established the belief amoung some circles that squatting deep is bad for knee ligament stregnth. Later studies fail to replicate these results.

Overall there is very little evidence to indicate that squatting deeply can cause the kind of knee injury in healthy individuals that many people worry about. In fact, the weight of evidence seems to be to the contrary. Studies indicate that deep squats seem to have no adverse effects at all on knee ligament streghth and one study suggests that they may actually strengthen the knee joint capsule in the long term if preformed correctly.

ant by a squat (she was Spanish, and aparently they don't have a word for it). So I preformed a full bodyweight squat, like so.

Here is what I look like on a Thursday evening.

The conversation then proceeded like so.

Her: "But my basketball coach in Spain and in this country say that you shouldn't let your knee go further forward than your toes when squating..."

"...Squatting so deeply is bad for your knees"

She then went onto demonstrate a half squat (like the above image but only half way down instead of the top of the legs being parrallel.)

Me: "I'm sure your basket ball coach is very good, but on this subject he is incorrect"

(This carried on back and forth for about 15 minutes)

Her: "So you are right and the whole world is wrong, yes?" (sarcasm)



The whole world? Really?... As in everybody?


Any stregnth and conditioning coach worth his salt will tell you that full squats with proper technique do not harm the knee. Far from it, in fact. Full squats stregthen the ligaments around the knee and 

Half squats



Klein, K. (1961). The deep squat exercise as utilized in weight training for athletes and its effects on the ligaments of the knee. Journal of Applied Physical Medicine and Rehabilitation, 15(1), 6-11

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Reader Comments (1)

It's so true about people squatting in other countries. I will never forget my approach by train into Mumbai station one morning - the banks were lined with people squatting. While this was for a particular reason (!), everyone seems to sit in the squatting postion for long periods of time in India.

July 2, 2012 | Unregistered CommenterRosey Davidson

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