Knees Out Or Knees In When You Squat?

Out (left) versus in (right)

Here is a post that will perhaps change the way you squat. It depends on what area you want to work on. Previously, some physiotherapists and personal trainers hated me for saying that you can let your knees move forward when you squat. Most, if not all, personal trainers teach their clients that it is taboo to let your knees move forward while squatting, They get their patients or clients to stick their bums out instead.

Those same physiotherapists and trainers may be aghast if I suggest squatting with your knees pointing in (gasp!) or pointing out. 

The author recruited 14 males and 18 females for the squatting study (Chiu et al, 2024). Using 3D motion cameras and force platform meausures, normal squats required hip extensor, adductor and lateral rotator net joint movements (NJM). The gluteus maximus muscle exerts hip extensor and lateral rotator moments. The adductor magnus (pictured below) exerts hip extensor and adductor moments. Both muscles combine meet hip demands contributing to hip extensor NJM.

When squatting with hip in lateral rotation (feet pointing outwards), there was smaller hip extensor, lateral rotator and larger hip adductor NJM than normal squats. This loads the adductor magnus.

Medial rotation squats (feet pointing inwards) had smaller hip extensor and adductor NJM and larger hip lateral rotator NJM than normal squats. This loads the gluteus maximus.

Likewise if you stick your bum out when you squat, you are engaging more of your bum (Gluteus Maximus) muscles. If your let your knees move forward when you squat, you are definitely using your thigh (quadricep) muscles. If you want to increase hip adductor (adductor magnus) work, squat with your knees out. It just depends on what muscles you want to engage or work harder. Try it yourself.

There is definitely no real need to restrict forward knee movement when you squat. It's one of the biggest training myths ever. You can add squatting with your knees pointing inwards and outwards to the list of myths as well. 

This information should 'challenge' some old school "perfect squat" gurus.

Reference

Chiu LZF. "Knees Out" Or "Knees In"? Volitional Lateral Versus Medial Hip Rotation During Barbell Squats. J Str Cond Res. 38(3): 435-443. DOI: 10.1519/JSC.0000000000004655.

Who Says Your Knees Cannot Come Forward When You Squat

For almost as long as I have been working as a physiotherapist (> 20 years), I have often heard other physiotherapists, trainers, strength and conditioning coaches tell patients that it's wrong to let their knees come forward when performing a squat. That by doing so, they will damage their knees. In fact, I've had many arguments/ disagreements with my ex colleagues at Sport Singapore (formerly Singapore Sports Council) regarding this.

To which I say that it's one of the biggest training myths ever. Yes, that your knees should not travel forward past the toes during a squat is definitely a myth.

In a study by Fry et al (2003), the authors looked at how joint forces at the knees and hips changed when restricting forward knee movement during a squat. What the authors found was that squatting with restricted forward knee movement showed a 22% decrease in knee forces while increasing hip forces by 1070%!

Picture A- knee travels forward, B restricted knee movement

Hence, you're simply shifting the load from the knees to the hips and lower back when you restrict forward movement of the knee. This is a lot more work for your hips and back to absorb and is potentially more dangerous for your hip and back.

Yes, I do agree it's true that it does stress your knees more when you allow your knees to come forward while squatting. However, this is well within the normal limits of what the knees can handle (Schoenfeld 2010).

You go to any Crossfit gym and/ or watch any  Olympic weight lifters and you will see that in order to reach full depth in the squat, their knees will almost always have to go forward past the toes (see picture below). The Olympic weight lifters will often do that with very high loads too.

Picture from Irving Henson taken at The Pit

If you stick your bum out when you squat, you are engaging more of your bum (Gluteus Maximus) muscles. If your let your knee travel forward when you squat, you are definitely using your thigh (Quadriceps) muscles. It just depends on what muscles you want to engage more. Try it yourself.

Different types of squats will have different types of knee forward movement as well. Front squat, high bar back squat, low bar back squat and box squats just to name a few.

So now you know that there is no real need to restrict forward knee movement when you squat, especially if you want to load your quadriceps more. As long as you are not squatting excessively  and with a super heavy load like the Olympic weight lifters.

References

Fry AC, Smith JC and Schilling BK (2003). Effect Of Knee Position On Hip And Knee Torques During The Barbell Squat. J Strength Cond Res. 17(4): 629-633.

Schoenfeld BJ (2010). Squatting Performance And Kinematics And Their Application To Exercise Performance. J Strength Cond Res. 24(12): 3497-3506. DOI: 10.1519/JSC.0b013e3181bac2d7.

Now surely the knees have to come forward .... picture from Catalyst Athletics