Why do we cave in our knees when it doesn't really help?

[sbhikes]

I notice that I can recover from almost failing a squat where I'm caving in my knees by consciously remembering to shove my knees out again. The weight will almost shoot itself up out of the sticking point. So why is it that knees out is advantageous but hard to do and the instinctual thing is to cave in the knees which is not helpful?

[hamburgerfan]

https://www.youtube.com/watch?v=QBnMjeMYY40

[Eric Davis]

My understanding if knees are held out by abductors then your adductors aid in hip extension. If the abductors are relaxed, allowing the knees to cave, then adductors can't aid in hip extension.

[John Hanley]

I notice that I can recover from almost failing a squat where I'm caving in my knees by consciously remembering to shove my knees out again. The weight will almost shoot itself up out of the sticking point. So why is it that knees out is advantageous but hard to do and the instinctual thing is to cave in the knees which is not helpful?

Our bodies will do some really weird shit to find mechanical advantage (our spines will flex/hyperextend, knees buckle & twist). The knee-cave is our body's way of eliminating moment at the hip (in the lateral direction).

[Clay Simczyk]

I think the squat is not really a natural movement for the body to accomplish. This is why there's so much conscious effort on our part to perform it properly. The deadlift, for instance, is much more natural and much easier to learn.

[sbhikes]

The squat isn't natural? Do you even poop?

[Clay Simczyk]

Not while holding a steel bar on my shoulders, although, that's happened too now that I think of it.

StainzZz!

[Michael Wolf]

https://www.youtube.com/watch?v=QBnMjeMYY40

This video assumes the slight knee cave is an advantage, and then offers a demonstration. It doesn't explain, or even attempt to explain why that assumption is a good one. The West of Westside article he mentions in the video doesn't do so either.

I think Hanley's explanation is, well, actually an explanation:

Our bodies will do some really weird shit to find mechanical advantage (our spines will flex/hyperextend, knees buckle & twist). The knee-cave is our body's way of eliminating moment at the hip (in the lateral direction).

Now, the question is: is eliminating that lateral moment at the hip at that moment in the squat, more beneficial than keeping than knees out and allowing the adductors to contribute more to the movement? There's also the fact that, while allowing the hips to cave decreases that lateral hip to knee moment, it increases the moment arm between the bar and the knees. I don't know the answer for absolute certain, but given all that, I'm inclined to think that knees out is, ideally, better. But it's damn hard to do at a limit weight.

[Karl Schudt]

Imagine if someone cut your adductors. How would you stand up? You would have to have your knees in so your quads could do the work that your adductors would have done in hip extension.

[Philbert]

Based on limited understanding of biomechanics, I believe we do it to eliminate lateral moment at the hip, as John said above, in order to unload the adductors and shift more of the work to the quads. This is a natural response to heavy weight, to put the load directly on the strongest available muscle group. As one builds stronger adductors, and trains the body to lift with all the useable muscle groups working together, the tendency for the knees to go in does decrease.