We’ve all heard this before about squatting. “Letting your knees go over your toes during a squat is bad for your knee”. I’m here to tell you that is not true. Squatting is an essential human function. Getting in and out of a chair or a car, picking up something, or playing with your children can all involve a squat. People have been doing this for as long as they’ve been around. So where did the notion that letting your knees go past your toes is bad come from?
Well, it’s actually been shown when you let your knees go past your toes you get a 28% increase in forces at the knee joint. People saw this and thought that increased stress automatically means that it is worse for your joints. First of all, all stress isn’t bad. Stress is what we supply our bodies with when we want to adapt to a workout. Lifting weights? That’s stress. Running? That’s stress. Stretching? Yup, you guessed it. Stress. So as long as you are aware of the increased stress you can adapt and adjust as needed.
What happens when you let your knees go over your toes.
Also, when looking at squatting with knees behind the toes, yes you had a 28% decrease in stress at the knee joint but where does that stress go? Does it just disappear? Nope. It’s actually shifts over to the hips and low back. Now, since the hips are bigger muscles you would think they could handle a 28% increase in stress better right? I would actually somewhat agree with that. But it’s not just a 28% increase in stress. The hips/low back actually take a WHOPPING 1073% increase in stress. Is that a trade you would like to make? I hope not.
What happens when you don’t let your knees go over your toes
So when somebody tells you that, make sure you ask them why. There is a time and place to not let the knees go over your toes during a squat but in general it is a safe activity for people to perform!
Fry AC, Smith JC, Schilling BK. Effect of knee position on hip and knee torques during the barbell squat. J Strength Cond Res. 2003;17(4):629-33.