Everyone "knows" that knees going inwards in a squat is bad, right?

It means the glutes are weak or underactive, and it's not good for the knee.

But is it REALLY?

This episode is a deep dive into the biomechanical, epidemiological, and prospective research on knee alignment during squatting, jumping, running and hopping. Our goal is to answer 2 questions:

1. Does the knee going inwards indicate weak glutes?
2. Is the knee going inwards dangerous?

Links:

• Knees going in during a squat shifts load toward the glute max here
• Knee extensor effort rises with squat depth, hip extensor effort rises with load here
• Same depth-versus-load split found again in a separate study here
• In elite powerlifters, heavier loads shift the work from knee to hip here
• Elite powerlifters hit ~23x bodyweight at the knee joint at 90% of max here
• Weightlifters share load between hip and knee; powerlifters are hip-dominant here
• Sideways knee load in a barbell squat is a consequence of stance width, not a fault here
• Elite weightlifters produce MORE frontal plane hip moment than lower-level lifters, not less here
• Elite powerlifters vary widely in how they load their joints, so there is no one ideal form here
• Lifters who fail a squat above their max show reduced extension and lower muscle activity here
• The knee falls into valgus in ~77% of ACL injuries on video here
• But knee valgus does not predict who goes on to tear an ACL here
• And the drop jump test cannot predict ACL injury in elite players here

Mentioned in this episode:

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:: 00:05

Most of us were taught that if a client's knees go inward as they squat or lunge,

:: 00:10

that means two things, weak glutes and they're increasing the injury risk to the knee.

:: 00:14

And because of those things, most of us have been taught and probably still

:: 00:18

do, Q, knees out during a lunge or squat, or at least knees not in.

:: 00:24

And I taught that for years. I've had my hands on the outside of a client's

:: 00:27

knees, ask them to push outwards into my hands as they squatted probably hundreds of times.

:: 00:34

But a deeper look into the literature actually reveals some very surprising

:: 00:40

things and so I'm going to test both of those claims,

:: 00:43

in this episode and walk you through the literature and by those two claims

:: 00:47

what I mean is number one knees in during a squat or lunge does that indicate

:: 00:51

weak glutes and number two is it dangerous for the knee all right so,

:: 00:57

the reason I started doubting this in the first place, if your knees go in,

:: 01:02

that indicates weak glutes,

:: 01:06

is that some of the strongest squatters on earth do that exact thing.

:: 01:14

Go to YouTube and type in Olympic weightlifting or powerlifting and you will see.

:: 01:25

Elite strength athletes, some of the best people on the planet,

:: 01:30

stand up out of a deep squat with a barbell that can be double or in some cases

:: 01:36

triple their body weight and with,

:: 01:42

a lot, like a substantial fraction, somewhere around half I would say,

:: 01:48

of elite lifters, their knees are.

:: 01:54

Obviously move inwards quite a significant distance as they stand up from a deep squat.

:: 02:02

And so if somebody is squatting two to three times their body weight and their knees go in.

:: 02:14

It's really hard for me to believe that that's caused by weak glutes.

:: 02:19

So something else is probably going on now. This is an observation. It's not proof.

:: 02:24

But that is what made me look closer at this question, and it's not the answer,

:: 02:29

but it's what prompted me to really deep dive into this.

:: 02:33

Now, I can hear what some of you are probably thinking, which is that,

:: 02:37

well, that's just compensation. When your knees go in under extreme heavy load,

:: 02:43

that's form breaking down under a load that's too heavy. And hold that thought.

:: 02:48

I want to bookmark that, and I want to come back to it a little bit later in

:: 02:52

the episode, because I think that's exactly backwards. And I think it's the

:: 02:55

most interesting thing in this episode. So just hold on to that thought about

:: 02:59

the compensation. All right.

:: 03:02

Before of the rest of this episode, though, will make sense,

:: 03:06

we need to agree on a couple of pieces of,

:: 03:09

anatomy and biomechanics, which is which muscles are primarily responsible for

:: 03:15

lifting you up out of the bottom of a squat.

:: 03:18

And I'm going to just say squat in this episode, but really it's any combined

:: 03:25

hip extension, knee extension movement.

:: 03:27

So that could be a squat, it could be a deadlift, which might not be a powerlifting

:: 03:33

competition move, it might be just lifting, shopping up off the floor,

:: 03:37

which is combined hip extension plus knee extension.

:: 03:39

Might be a lunge, it might be a split squat.

:: 03:44

There are myriad movements and formal fitness exercises that involve a combination

:: 03:51

of hip extension, knee extension.

:: 03:54

And so I'm just going to say the word squat, so I don't have to list all of

:: 03:57

the exercises every time. All right, but this applies to all of the above.

:: 04:01

All right, so which muscles lift you up out of the bottom of a deep squat, out of a squat?

:: 04:06

So as you stand up out of a squat or lunge, you're doing hip extension and knee extension.

:: 04:13

So the main muscles that are loaded, the main muscles that produce the primary

:: 04:17

force are the hip extensors and the knee extensors.

:: 04:23

Now, in a deep squat, especially below 90 degrees of knee flexion,

:: 04:28

so when your hip is below your knee, the main hip extensors.

:: 04:36

Are the glute max, gluteus maximus, and the adductor magnus,

:: 04:41

which is the largest of the adductor muscles.

:: 04:44

Now, I was taught in my original Pilates training, and probably you were taught

:: 04:50

in your original Pilates training, that the hip extensors are the glutes and hamstrings.

:: 04:58

And that is kind of true in that the, well, the glutes are hip extensors, that is 100% true.

:: 05:06

The hamstrings are hip extensors.

:: 05:12

They originate on the ischial tuberosity, which is posterior to the axis of

:: 05:19

rotation of the hip joint, so far so good.

:: 05:23

However, the hamstrings are all two joint muscles. They're both hip extensors and knee flexors.

:: 05:32

And during a standing up out of a squat, you are extending the hip and flexing,

:: 05:41

I'm sorry, extending the knee as well. You're extending the hip and extending the knee.

:: 05:46

Now, hamstrings are hip extensors and they're knee flexors. So as you stand

:: 05:52

up out of a squat, the hamstrings are shortening over the hip joint,

:: 05:56

but they're lengthening over the knee joint.

:: 05:59

And a couple of studies have actually examined what happens to the hamstrings

:: 06:04

during a squat and found that they don't change length. They essentially stay

:: 06:11

the same length throughout the squat movement.

:: 06:16

And I've done a couple of video posts on this, just showing a little flex band

:: 06:20

demonstration of the skeleton.

:: 06:21

It's a very simple demonstration to do that as the hip extends and the knee,

:: 06:25

extends, the distance between the ischial tuberosity and the tibial plateau

:: 06:32

stays pretty much the same. So the hamstrings work isometrically in a squat.

:: 06:36

And a squat is actually a very poor hamstring exercise for this reason.

:: 06:40

The hamstrings aren't primary force producers in a squat. They act isometrically.

:: 06:46

Their primary function is thought to be stabilization of the knee.

:: 06:50

They're synergists with the ACL. They prevent anterior shear of the tibia relative

:: 06:55

to the femur, and they also laterally and rotationally stabilize the knee along with the quadriceps.

:: 07:01

So in a deep squat, the main hip extensors do not include the hamstrings.

:: 07:08

Squats, lunges, all of those types of hip extension, knee extension moves are

:: 07:14

not great hamstring exercises. To work the hamstrings effectively,

:: 07:17

now of course hamstrings are active during these movements, but they're not

:: 07:20

the primary mover, so they're not under massive load.

:: 07:23

And so to work the hamstrings effectively, you need to isolate either the hip

:: 07:27

or the knee. So you need to do isolated knee flexion or isolated hip extension

:: 07:31

with the knee held constant.

:: 07:34

But in a squat, the hamstrings are isometric. So the main hip extensors as you

:: 07:39

stand up out of a squat, especially a deep squat below 90 degrees,

:: 07:43

are gluteus maximus and the adductor magnus.

:: 07:47

Not the hamstrings. All right.

:: 07:50

So one more detail that matters is that the gluteus maximus has both upper and lower fibres.

:: 08:03

So it has the iliac fibers, the fibers that attach to the crest of the pelvis,

:: 08:11

and it has the sacral fibers, the fibers that attach to the sacrum.

:: 08:16

Iliac fibers are the upper fibers, sacral fibers are the lower fibers.

:: 08:23

And,

:: 08:26

the upper fibers, especially, I mean all of the fibers, but especially the upper

:: 08:30

fibers, are a powerful lateral rotator of the hip.

:: 08:37

And when your hips are flexed,

:: 08:43

lateral rotation is the action that pushes the hip outwards.

:: 08:50

It's not actually true abduction. So if you think about you're squatting down,

:: 08:55

you're at the bottom of a squat, if you push your knees out,

:: 09:00

it is not true abduction, it is hip lateral rotation that you're doing,

:: 09:07

combined with abduction. So when you move your knees out in a squat,

:: 09:13

it's the gluteus maximus amongst

:: 09:16

the other hip lateral rotators that is primarily responsible for that.

:: 09:21

So if the knees go in, it's internal rotation. If the knees go in,

:: 09:26

sorry, it's internal rotation.

:: 09:28

All right, so...

:: 09:33

In 2012, a.

:: 09:38

Study by Braynton and colleagues in the Journal of Strength and Conditioning

:: 09:42

Research found that knee extensor effort, or in other words,

:: 09:47

the quadriceps, goes up as you go deeper into a squat.

:: 09:52

So if you go halfway into a squat and then you go deeper and deeper into a squat,

:: 09:57

the quads work more the deeper you go.

:: 10:01

Whereas with hip extensors so the gluteus maximus and the adductor magnus that is also true.

:: 10:11

And with hip extensors as you add more load,

:: 10:16

hip extensor load goes up whereas as you add more load the quad load doesn't

:: 10:20

go up so you can do body weight squats and as long as you do them deep your

:: 10:26

quads will be very close to maximally loaded as long as you do enough reps.

:: 10:31

Whereas with glutes and adductor magnus, you're going to load them more effectively

:: 10:36

by going deep, but also they are more and more active and there's more load on them as you add,

:: 10:46

more external load to the movement.

:: 10:48

So a heavily loaded deep squat is going to bias to glutes and adductor magnus,

:: 10:53

whereas a lightly loaded squat is going to bias more to quadriceps.

:: 10:58

Now, both movements will involve all of those muscles, but the load shifts where

:: 11:03

the external load influences where the internal load is born.

:: 11:10

All right, so if you want to load the quads, just go deeper.

:: 11:16

If you want to load the glutes and adductor magnus, go deeper and heavier.

:: 11:23

All right, so this is the 2024 study that really was, as far as I'm aware,

:: 11:31

the first bit of evidence to really look at knees going in and how that impacts hip and knee talk.

:: 11:38

So this is Lauren Chu, 2024, the General Strength and Conditioning Research.

:: 11:43

They had 32 people, 18 women, 14 men, squatting with a loaded barbell three different ways.

:: 11:48

So they squatted in their natural way with no instruction.

:: 11:52

So they just said squat, and then they deliberately cued them to squat with

:: 11:58

their knees in, and then they deliberately cued them to squat with their knees

:: 12:03

out. So three different ways, just no cue, then knees in, then knees out.

:: 12:07

And they had a force plate underneath their feet, so measuring how much ground

:: 12:11

reaction force, how hard they were pushing into the ground, plus motion capture,

:: 12:16

to calculate the moments, the forces, at the hip and knee.

:: 12:21

And what Lauren Chu found, that the knees-in squats produced.

:: 12:28

Smaller hip extensor forces, smaller adductor forces, and larger hip lateral

:: 12:34

rotator forces than normal squats.

:: 12:38

So knees-in produced larger hip lateral rotator forces than normal squats.

:: 12:44

And these were not just statistically significant, they were large enough to

:: 12:47

actually matter in practice.

:: 12:49

And so just thinking about that in the context of the anatomy we just talked through is that,

:: 12:55

that combination of knees in deep squat biases the load towards the iliac fibers of the glute max,

:: 13:05

or really all of the fibers, but it's particularly the iliac fibers of the glute

:: 13:09

max and away from the adductor magnus.

:: 13:13

So as you go into a deep, heavily loaded squat, you're increasing load on the hip extensors.

:: 13:18

As your knees go in...

:: 13:21

You decrease load on hip extensors, increase load on hip lateral rotators.

:: 13:26

Now, adductor madness is a hip extensor, so you're decreasing the load on that as your knees go in.

:: 13:31

Glute max is a hip extensor and a lateral rotator.

:: 13:36

So as you decrease load on hip extensors and increase load on lateral rotators,

:: 13:39

you actually don't decrease total load on the glutes, okay, because the load has to go somewhere.

:: 13:46

And because as you decrease load on the adductor magnus and increase load on

:: 13:53

the lateral rotators, well, that load just shifts more to the glute max.

:: 13:57

So you're shifting load essentially away from adductor magnus and towards glute

:: 14:00

max. And what they found with the knees out condition was the inverse.

:: 14:04

So as you squat with your knees out, you decrease load on the external rotators

:: 14:09

and increase the load on the adductors. So knees out actually biases towards adductor magnus.

:: 14:16

Because think, knees out in a squat, as you stand up and straighten your legs, your knees adduct.

:: 14:27

So you're using your adductors to stand up. Whereas if you start at the bottom

:: 14:32

of the squat with your knees in, as you stand up, your knees,

:: 14:36

your legs straighten, your knees abduct.

:: 14:39

So you're working your abductors, or in this case, it's actually the lateral

:: 14:43

rotators that are doing that action.

:: 14:48

Okay, so that study really contradicts the folk wisdom that knees going in during

:: 14:57

a squat indicates weak glutes.

:: 15:00

In fact, it loads the glutes more, knees going in in a squat,

:: 15:05

according to this study.

:: 15:10

And why would we want to load the glutes more? Well, why would people unconsciously

:: 15:15

squat with their knees in and load the glutes more? well, if the glutes are

:: 15:18

stronger and you wanted to produce more power,

:: 15:24

that would do it. You would become more powerful, you'd produce more force.

:: 15:28

A couple of other things, this is back from the 2022 episode,

:: 15:34

and so this is more speculation, that as your knees go in, you might be pre-stretching,

:: 15:42

the glute max to produce more force.

:: 15:44

Just like when you throw, you know, you automatically draw your hand backwards

:: 15:49

beforehand, or when you go to jump up, you automatically kind of squat down

:: 15:52

a little bit first. We pre-stretch the muscles to produce more force.

:: 15:56

We might be doing that on the way up out of a squat with the knees go in.

:: 15:59

All right. So now, I'm not telling you to cue everyone knees in in a deep squat.

:: 16:08

Quite the contrary, I think you should actually stop cueing knee position at

:: 16:12

all, except in very specific situations that I'll come to later.

:: 16:16

Neither in nor out, just don't cue knee position.

:: 16:21

All right, so deep-bladed squats and lunges, load the glutes in,

:: 16:24

Dr. Magnus, very effectively.

:: 16:26

You don't need to cue any kind of knee position to load the glutes,

:: 16:29

just load the movement deep and heavy, and you will effectively target all of those muscles.

:: 16:35

All right. So that is the literature I found on muscle recruitment and loading with regard to knees in.

:: 16:43

So the only evidence we have points to knees going in, actually loading the

:: 16:50

glutes more, not being a sign of quite weak or lazy glutes.

:: 16:56

All right. Next idea is, and this is one that really surprised me.

:: 17:00

In the sport with the heaviest squats on earth, powerlifting,

:: 17:04

almost nobody has measured knee position in the frontal plane.

:: 17:06

That's side-to-side movement of the knees.

:: 17:10

When I went looking for research on elite powerlifters and weightlifters,

:: 17:14

there's a lot of it, and it is good in terms of biomechanical research.

:: 17:18

So Pertzer and colleagues, 2026 in scientific reports, put 29 national and international

:: 17:23

powerlifters through 3D motion capture, squatting at 70% to 90% of their backs.

:: 17:28

And they found that as the load goes up, the hip takes more and more of the

:: 17:32

work while the knees and ankles maintain the flat work rate.

:: 17:36

So that just mirrors what I said before, which is that as you add load to a

:: 17:41

squat, the hip extensors are preferentially loaded more, like proportionately,

:: 17:49

they take more of the load.

:: 17:52

Uh, Rettenberg in way back in 1996, found that weightlifters and powerlifters

:: 17:58

split the load differently. Weightlifters share between hip and knee pretty

:: 18:02

equally, whereas powerlifters are more hip dominant.

:: 18:05

And that is to do with where I think where the, where they hold the bar on their

:: 18:08

back. So powerlifters tend to hold the barbell lower on their back.

:: 18:12

So the center of mass is lower. So they do more of a torso lean in their squats.

:: 18:17

Whereas weightlifters tend to hold the bar higher on their back.

:: 18:20

So they stay more upright as the center of mass is higher.

:: 18:25

But here's the thing, almost all of the research on weightlifters and powerlifters

:: 18:30

and biomechanics of the knees and hips and torso,

:: 18:34

is in the sagittal plane, which means they look from the side and they look,

:: 18:40

at knee and hip and spine and ankle flexion extension.

:: 18:45

There's essentially no research looking at frontal plane movement biomechanics

:: 18:53

in powerlifters and weightlifters. So in other words, leg valgus or knee valgus,

:: 18:57

the knees going in or out during a squat.

:: 19:00

That research essentially hasn't been done. Now, there are several studies I

:: 19:04

found that collected 3D data on elite lifters,

:: 19:11

but all of those studies only published flexion and extension moments.

:: 19:16

Sideways knee movement, the thing that we're talking about today in this episode,

:: 19:20

And the thing that we typically cue most with relation to safety just is basically

:: 19:27

unmeasured and unreported in this study.

:: 19:28

And the closest study I found is Lati and colleagues, 2018, in the Scandinavian

:: 19:33

Journal of Medicine and Science in Sports.

:: 19:35

And they did report frontal plane knee movement. So in other words,

:: 19:39

abduction, adduction, or knee moving in or outwards, in a loaded barbell squat

:: 19:44

in a wide versus a narrow stance.

:: 19:50

But they reported knee lateral movement lateral medial movement,

:: 19:56

as a consequence of how wide you stand, not a fault to be corrected.

:: 20:01

So just think about it, like if you squat with a very, very narrow stance,

:: 20:05

like your feet almost touching together, your knees almost go straight forwards,

:: 20:09

right? So there's very little lateral movement, you know, medial or lateral

:: 20:13

movement of the knees as you go up or down.

:: 20:15

Whereas if you stand with your feet, you know, one and a half times shoulder

:: 20:18

width apart and your legs turned out, as you squat down, your knees move laterally,

:: 20:24

and as you stand up, your knees move medially.

:: 20:27

Even if your knees don't go into any kind of valgus, just because you're standing

:: 20:33

in a wider stance, your knees move a little more laterally. So that's what they

:: 20:36

looked at. They didn't actually look at valgus. Yeah.

:: 20:39

All right, so the final study I found in relation to this on powerlifters was

:: 20:46

a group called PERD CELL in 2025.

:: 20:50

They estimated that at 90%.

:: 20:55

Of their max, elite powerlifters generate peak joint contact forces,

:: 21:02

of over 23 times body weight at the knee joint and nearly 27 times body weight

:: 21:09

at the patellofemoral joint, the kneecap, the joint between the patella and the femur.

:: 21:15

And so those forces are massive. And if you just go look on YouTube and type

:: 21:24

in like powerlifting squat world record, that kind of thing.

:: 21:31

You will see that elite powerlifters frequently, I would estimate roughly half

:: 21:37

of elite powerlifters have extremely visible knee valgus as they stand up out of heavy squats.

:: 21:45

And these people have, according to Pertzel, 23 times body weight going through

:: 21:52

each knee, each knee, and they're doing valgus.

:: 21:57

And these people have done thousands of reps of squats. To be able to squat

:: 22:02

triple your body weight, you have to do thousands of reps over a large number

:: 22:06

of years in order to become that strong.

:: 22:08

And so that doesn't seem to be hurting their knees.

:: 22:12

Now, don't have research on that, but seems fairly logical to me. All right.

:: 22:17

Now, with that in mind, let's come

:: 22:19

back to the thought I mentioned earlier that knees go in at 90% of max.

:: 22:24

And so that that is a compensation. That's form breaking down under too much load.

:: 22:31

And I want to take that apart because one of the things that on the surface

:: 22:36

seems eminently sensible, but the closer you look at it, the less it makes sense.

:: 22:44

So start with the word compensation. That's not a description of what happens.

:: 22:49

That's a judgment about why it happened.

:: 22:54

The neutral description of the knee moved inwards would be, simply to say,

:: 22:59

the knee moved inwards. That describes what happened.

:: 23:03

Compensation is a story about why the knee moved inwards.

:: 23:08

I think this is a culturally constructed meaning. It's not based on what we

:: 23:12

know about biomechanics.

:: 23:13

So we have a notion of ideal form that, in my opinion, is largely aesthetic.

:: 23:23

If you think of ideal form in pretty much any movement,

:: 23:27

we think of straight lines, even curves, smooth movement, symmetry.

:: 23:35

So we teach that. Now, there's nothing wrong with any of those things.

:: 23:42

But liking how a movement looks is not the same as knowing that it's safer or more efficient.

:: 23:53

Now let's bring load into the picture. At low load,

:: 23:59

we have lots of movement options. At high loads, we have very few options.

:: 24:06

Think about it. If you lift a pen off the floor, there's a million ways you could do it.

:: 24:12

You could have your arms straight or bent. You could use just two fingers or your whole fist.

:: 24:18

You could hold it close to your body or far away.

:: 24:22

You could bend your back or your knee or your hip or lift your heels off the

:: 24:26

floor there are so many ways you could lift that pen,

:: 24:30

whereas to lift a 30 kilogram or 66 pound dumbbell off the floor you'd have

:: 24:37

a lot fewer options you'd have to use a power grip like put your whole fist

:: 24:41

around the handle and grip it hard,

:: 24:46

you'd have to hold it close to your body you wouldn't be able to hold it with

:: 24:49

your elbow straight at arm's length.

:: 24:52

You'd have to get your back and hips involved.

:: 24:57

As the load increases in any movement, you have fewer and fewer options about how to do the movement.

:: 25:05

When you are squatting one and a half times your body weight,

:: 25:11

you can't.

:: 25:16

You have a lot fewer options about how to consciously arrange your body.

:: 25:20

You just have to use whatever works best, what allows you to produce the most

:: 25:25

force to do that movement.

:: 25:27

So when we're practicing low-load movements, like squatting with a PVC pipe

:: 25:35

on your back, like they do at CrossFit.

:: 25:37

I've seen this happen a fair bit at CrossFit, where they practice squatting

:: 25:41

or Olympic lifting usually with a PVC pipe.

:: 25:44

It's basically the same shape as a barbell, but weighs essentially nothing, like a broomstick.

:: 25:51

Well, in that situation, you can squat a thousand different ways.

:: 25:54

And so when we do it in Pilates with no external load apart from the body weight,

:: 25:59

you can squat or lunge a thousand different ways.

:: 26:01

Knees in, knees out, back bent, back straight, arms up, arms down,

:: 26:06

hip distance apart with your feet, shoulder distance, double shoulder distance,

:: 26:11

feet together. There's so many ways you could do it.

:: 26:17

So at low load, your movement is barely constrained by the task at all.

:: 26:21

You've got enormous freedom. We can generally achieve something that looks similar

:: 26:26

to our aesthetic ideal of smooth, symmetrical movement with straight lines and even curves.

:: 26:32

Now, put 90% of your one rep max on your back.

:: 26:37

How many ways can you complete that lift? Well, almost none.

:: 26:42

The task has now, the load has constrained your options.

:: 26:48

There's a very small set of movement solutions that will get that bar up,

:: 26:54

and if you don't find one of them you don't get to complete the lift so under

:: 26:58

a very heavy load like that and powerlifting research does show this.

:: 27:06

Your nervous system finds a solution it arranges your limb positions etc and

:: 27:11

your timing to produce the force required and if you lift the load then by definition,

:: 27:17

that solution that strategy worked it produced enough force,

:: 27:22

now we do see that power lifters as load increases they converge on a more similar

:: 27:31

set of timing between hip and knee and spine extension,

:: 27:35

okay so they might do different a much more varied set of timings under low

:: 27:40

low but as high as load increases we see the time is converged now they're not

:: 27:43

identical but they do converge quite substantially.

:: 27:47

So if your technique changes as you go heavier,

:: 27:53

is that truly a compensation or are we just abandoning the artificially imposed,

:: 28:00

notion of ideal form that we

:: 28:03

can afford when we're doing a light load because we have so many options?

:: 28:08

Whereas when we're lifting a heavy load, we actually have to do it the most efficient way.

:: 28:12

And so your nervous system, your primator cortex, your spinal cord,

:: 28:17

et cetera, just says, okay, well, I'm just going to take over here because you're

:: 28:20

obviously doing it wrong with your idea of keeping everything straight and neutral

:: 28:24

and smooth and everything.

:: 28:25

And I'm just going to arrange the body and engage the muscles in such a way

:: 28:30

to produce the maximum force.

:: 28:32

So is it a compensation? Because compensation implies there's a weakness in

:: 28:36

one area, so we engage a different area to make up for it. where another way

:: 28:39

of stating the exact same strategy is you engage the areas that are able to

:: 28:43

produce the most force, the most efficiently.

:: 28:46

And at 90% of your max, there isn't a better option available.

:: 28:49

That's the whole point of lifting close to your maximum, which means the thing

:: 28:53

we call form breaking down or compensation might be closer to the opposite.

:: 28:57

It might be your best form, the form that lets you produce the most force.

:: 29:02

And now flip it around because this is the bit that changed my mind if low load

:: 29:07

lets you move a thousand different ways and high load lets you move almost one

:: 29:11

way then which of those ways is the arbitrary way.

:: 29:17

The form we teach with no load or body weight is a choice we picked it it's

:: 29:23

like dance you can dance five ten fifty a hundred different ways and some of

:: 29:26

them are more aesthetically pleasing than others.

:: 29:30

We picked it not because it's forced on us by the task, but because at that

:: 29:34

load, nothing is forced on us. The form that shows up at 90% of your maximum

:: 29:39

is not an aesthetic ideal.

:: 29:43

It's the biomechanical imperative that we have to move in that certain way if

:: 29:48

we're going to complete the task. So, I.

:: 29:56

Just want to add in one last little caveat on this, which is I don't want to overstate this.

:: 30:06

Now, because everybody has different limb length segment, some people's femurs

:: 30:10

are longer or shorter relative to their tibias. We have different joint surface

:: 30:13

angles. We have different hip socket angles and depths and different femoral neck angles, et cetera.

:: 30:19

We have different muscle insertion points. We have different relative strengths

:: 30:22

of different muscles in our body.

:: 30:25

A taller person bending over to pick up something will have to bend more than a shorter person.

:: 30:30

So there is no one ideal form for everybody.

:: 30:38

But each of us, given our unique set of limb length ratios, muscle insertions, etc.,

:: 30:44

we'll have some ideal, our own version of ideal form for a given movement,

:: 30:50

picking something up from a given height at a certain load.

:: 30:55

But the best alignment for producing force on this rep is not necessarily the

:: 30:59

same thing that has the best for your knees in 20 years.

:: 31:02

And these are separate questions, and I don't want to blur those two questions.

:: 31:06

But what I'd say is that nobody has shown that it's harmful either.

:: 31:11

In fact, the evidence we do have shows no harm. And one more thing worth knowing.

:: 31:16

Um, Cholawicki et al measured national class powerlifters, uh,

:: 31:19

back in the early 1990s, 1990, 1991, something. And he found large variability

:: 31:25

in how they loaded their joints.

:: 31:28

Um, and so there's no one ideal form even amongst the very best. All right.

:: 31:34

So that's joint loading. Now I want to move on to the, to the,

:: 31:37

the specifically to knee injury and most common knee injury being,

:: 31:42

uh, anterior cruciate ligament injury.

:: 31:43

And that is the injury, the knee injury, that is most commonly associated with

:: 31:48

knee valgus or knees going in.

:: 31:51

And so, yeah, this is the part where I don't want to leave you thinking that

:: 31:55

knee position never matters. There is a situation where it does.

:: 31:59

All right. So a systematic review by Gopinath and colleagues in 2024 in the

:: 32:04

Journal of Arthroscopy pulled 13 video analysis studies covering 542 athletes, mostly in soccer.

:: 32:13

And then they fell and they looked at the moment, the instant,

:: 32:18

because soccer is televised, and they looked at the instant when people injured their ACL.

:: 32:23

They actually froze the frame and looked at what was the position of the hip,

:: 32:29

the knee, the ankle, the torso in the instant when the ACL was injured.

:: 32:34

And they pulled 13 studies covering over 500 athletes and they found that the

:: 32:42

knee was in valgus, so in other words, knee was inwards, in about 77% of those injuries.

:: 32:49

So knee valgus does have an association with, in the moment,

:: 32:55

of ACL injuries. It seems to be the position in which the ACL is injured. But here's the part.

:: 33:03

That actually doesn't add up with that.

:: 33:06

Researchers have tried to use knee valgus in squats and jumps and things to

:: 33:12

predict who will get injured, and that has not worked.

:: 33:15

So a meta-analysis by Kronstrom et al. in 2020 in the BMC musculoskeletal disorders,

:: 33:22

they pulled nine prospective studies.

:: 33:24

So those studies where they looked at people doing depth jumps,

:: 33:27

so basically they'd stand on a box and they'd jump down and they look at how

:: 33:30

much their knees go in when they land.

:: 33:33

And then they follow those people over the next year and they see like who gets

:: 33:36

an ACL injury and who doesn't.

:: 33:38

And what they found was there was essentially no correlation between knee abduction

:: 33:43

angle, so that's how much valgus they had,

:: 33:47

or peak knee abduction moment, so the force, the knee valgus moment,

:: 33:54

neither of those things had any correlation with future ACL injury.

:: 33:59

So when you jump off a box and land.

:: 34:02

With high impact, okay, there's no correlation with whether or how much your

:: 34:07

knees go in and subsequent ACL injury.

:: 34:12

Cross Hogg and Ed Al in 2016 in the American General Sports Medicine followed

:: 34:16

710 elite female soccer players,

:: 34:20

and they concluded that the drop-jump test, the one I just described jumping

:: 34:23

off a box, cannot predict ACL injuries.

:: 34:28

So valgus is, that's the knee going in, is part of the injury picture.

:: 34:33

It's present in 77% of the moment of injury, but it's not useful as a screening test.

:: 34:39

So both of those things are true. In fact, when I look deeper into the ACL injury

:: 34:46

literature, looking at the mechanism, like the instant of injury,

:: 34:51

anterior tibial shear, so the tibia sliding forwards relative to the femur,

:: 34:58

so the tibia is the shin bone, the femur is the thigh bone, is the primary component of ACL injuries.

:: 35:04

And there are researchers who think valgus in ACL injuries happens in the milliseconds.

:: 35:11

After ACL rupture, not before.

:: 35:13

So that the valgus might be a result of the injury, not a cause of the injury.

:: 35:20

Now, this is still not what I would call settled science, but it is intriguing.

:: 35:28

Now, the loading matters here very much.

:: 35:33

An ACL tear is a high-speed, high-force, multi-planar event that unfolds in about 40 milliseconds.

:: 35:43

A bodyweight squat or lunge on a reformer is not that on any axis.

:: 35:51

So at the loads and speeds we work at in a studio, and in fact,

:: 35:55

even during a three times body weight squat in powerlifting,

:: 36:01

a knee that moves inwards is not any kind of danger.

:: 36:08

It's not a safety problem that needs to be corrected.

:: 36:11

Cueing knees out probably does have a place in ACL rehab, in hopping and cutting.

:: 36:18

And I'm sorry, I can't remember the name of the research, but I did find a paper that found that.

:: 36:25

Where drop jump, knee valgus wasn't associated with subsequent ACL injury,

:: 36:30

actually knee valgus during cutting and vertical hopping was.

:: 36:34

So cutting is where basically an athlete changes directions,

:: 36:38

like rotates on one, like you It basically turns left or right whilst running fast.

:: 36:44

So you're running and then you pivot to the left or pivot to the right,

:: 36:48

and that is called cutting.

:: 36:50

And so knee valgus during that high-speed running change of direction does predict ACL injury.

:: 36:57

So if you're rehabbing ACLs or you're preparing athletes to prevent ACL injuries,

:: 37:04

cueing knees out during cutting probably is valuable.

:: 37:10

And cueing knees out during hopping, although hopping is not really a thing

:: 37:16

athletes do, but if hopping is a core part of ACL rehab,

:: 37:22

and so cueing knees out during hopping probably is something that is valuable

:: 37:28

and that I will continue to do at this point for ACL rehab or prehab, you know, prevention.

:: 37:34

All right. So in conclusion, a knee leaning in...

:: 37:44

You know, looks like weakness because we've been culturally conditioned,

:: 37:51

essentially, educated that that's the case with words like collapse, compensation.

:: 38:00

The force literature, however, says that it just may be the glutes doing more,

:: 38:05

not less, as that happens.

:: 38:08

And in the sport where it would matter most, powerlifting and Olympic weightlifting,

:: 38:12

almost nobody has ever bothered to measure it. They don't even worry about it.

:: 38:16

It's just a common thing that happens. Half of athletes do it.

:: 38:20

And the thing we call form breaking down under load may be the closest thing

:: 38:26

to true ideal form for that person in that moment because it's the only form the task allowed.

:: 38:31

A lot of what we're taught in Pilates school and on social media and weekend

:: 38:34

workshops encourages us to look at the body and decide which part is failing

:: 38:41

or compensating under the assumption that there is such a thing as universal ideal form.

:: 38:46

Usually, we cannot see that from the outside. And sometimes what we're calling

:: 38:51

a failure, compensation or

:: 38:53

weakness or limitation, is the body solving the problem most efficiently.

:: 38:58

We can't see people's relative limb segments very easily. We can't see their

:: 39:02

limb segment lengths very easily. We can't see their muscle attachments.

:: 39:06

We don't know the proportion of fast versus slow twitch fibers in each of their

:: 39:11

muscles. And so we can't look at somebody and know their ideal form for a given movement.

:: 39:19

Their nervous system does have all of that information though and can decide that.

:: 39:27

What we can do is understand the basic biomechanics load and movement well and

:: 39:33

coach the outcome of the movement rather than a specific alignment.

:: 39:39

All right. I hope you found this at least interesting.

:: 39:44

I'm going to put a bunch of those studies link in the show notes.

:: 39:50

And if you like this episode and you like reading books,

:: 39:57

check out my book on amazon it's called strengthen the person not just the body

:: 40:03

part and it is about using science to rehabilitate or prehabilitate pretty much any injury,

:: 40:13

all right thanks dear listener much love and i'll see you in the next one.