What does modern medical science tell us about bending the knee with bodyweight?

[SatoriMovement]

I am not a physical therapist, but I have a strong interest in using the body in ways which are anatomically sound. I see so many health-maintenance fads which are encouraging people to harm their bodies by using them improperly.

What is the latest word regarding knee bending exercises with bodyweight? I have heard that deep squats are unhealthy, and then also that they are good for the body. I have heard the same about deep squats on the ball of the feet. I have heard that the knee should never go past the toe when the heels are flat. Is any of that true?

What about with dance-specific knee bends like the plie? I have heard that grand plies are not good for the knees, but what about demi-plies(heels together, feet turned out, bending at the hips, feet stay flat on the ground, occasionally knees go past toes).

It seems there is conflicting information about all of this in the fitness profession, and I'd like to know what modern medical science says.

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[basupran]

When you go into too much knee flexion, you can reduce your tibio-femoral contact surface by around half. This increases joint contact pressures (pressure = force/area) and can lead to premature OA.

 

[Danae00]

What is the latest word regarding knee bending exercises with bodyweight? I have heard that deep squats are unhealthy, and then also that they are good for the body. I have heard the same about deep squats on the ball of the feet. I have heard that the knee should never go past the toe when the heels are flat. Is any of that true?

I'm not a physical therapist (nor have I even started school), but I have done a lot of looking into biomechanics for personal training purposes. So this is my totally non-professional opinion.

Assuming someone doesn't have any pre-existing problems with their knees, and you are using proper technique, then squats are very good for you. As far as how deep you can go, typically the recommendation is to go down until one of the following occurs: your thighs are parallel to the ground, your heels start to lift, or your back starts to round.

Some people will continue into a deeper squat if they can maintain proper technique, but I'm not comfortable with doing it myself. From what I understand as long as your knees are perfectly healthy there the risk is minimal. But my knees have taken a lot of abuse over the years so why risk it at all? Besides, I squat mainly for leg strength and once your knees flex more than 90 degrees you are then mainly working your gluts (which already get a good workout in my routine).

I have never seen anyone doing squats on the balls of their feet before, but my gut tells me that is not a good idea. And yes, you should avoid allowing your knee to come forward past your toes in exercises like the squat and lunge.

 

[DancerFutureDPT]

What about with dance-specific knee bends like the plie? I have heard that grand plies are not good for the knees, but what about demi-plies(heels together, feet turned out, bending at the hips, feet stay flat on the ground, occasionally knees go past toes).

From a ballet standpoint, the main concern is grand plie in second position. The thighs should never go past parallel (aka your butt should never be below your knees in the plane). That's the absolute farthest you should go routinely (of course choreography may call for something different...if you saw the last dance on SYTYCD tonight with Billy Bell he was violating all those rules, but it's not something done every day repeatedly). I always tell people not to go any farther down than your turnout allows. As soon as your foot starts to roll in, your knees lose their alignment (cave inward/in front of the second toe), then that's too far.

First position, etc, grand plie isn't as dangerous (as far as I know) since your heels do lift). All of this is assuming proper technique/turnout. I know people who were forced to have 180 turnout from a young age by their instructors who are now 18 and have horrid knee problems, because they weren't strong enough/didn't have the anatomical makeup to sustain that turnout, so they cheated using knee and ankle rotation.

I'm not sure why it's okay for a demi plie to go past the toes, but not for a squat. I'm assuming it's because of the turnout and the other muscles involved to maintain it, taking pressure off of the knees? I'm not sure though. I'll try to ask one of my dancer PT friends.

 

[atstudent]

I'm not sure why it's okay for a demi plie to go past the toes, but not for a squat. I'm assuming it's because of the turnout and the other muscles involved to maintain it, taking pressure off of the knees? I'm not sure though. I'll try to ask one of my dancer PT friends.

Simple answer.. when you squat you normally have weight on your back. Squatting is an exercise that I always emphasize with whatever athletes I'm working with. They need to sit back and keep the weight on the heels. Knees and toes aligned. Should be going just past parallel. In other words, when in the down position, a marble should be able to be placed on the quads and either stay put or roll toward the hip. Keep those knees behind or even with the toes to take that pressure off the knee joint.

You have to really work on making sure they don't allow their knees to buckle. Females especially tend to go into genu valgum when squatting and that's not a good thing. It takes practice, but everybody can get good at it if they work on it.

 

[MinnDasota]

I use squats all the time with my patients (both dancers and non dancers). Generally, I follow the principles of Gray Cook's Functional movement screens. A few things can limit someones deep squat. 1. weak core and gluts. 2. tight calves. 3. tight lats (when doing an overhead deep squat). When these are corrected, a correct deep squat can be accomplished without undue stress to the knees. Often, I will use some combination of a deep squat with a plie with my dancers while using knee valgus over correction (resistive band pulling the knee into valgus and forcing the dancer to engage her hip/gluts to keep her knee in the proper position). Along with quite a few other exercises that focus on proper hip and knee positioning, I get great results and the dancer usually returns to classes or performances quickly.

Most dancers are required to do plies and other moves that are unnatural to the general population. Thus, you have to work on getting them to fire the right muscles during these movements.

As a general rule with any squat/lunge/single leg activity, I make sure the hips stay level and pointed forward, knees stay in line with the hips and ankle, and toes pointed forward. I stay within pain free range but do have a goal of the thighs going at least parallel to the floor. I look at squats as a core/glut exercise and focus on achieving this, which in turn decreases the use of the quads and stress on the knees.

 

[SatoriMovement]

Well, this pretty much confirms my suspicions regarding squats.

As for the reference to "deep quats on the balls of the feet", these are sometimes called "hindu squats", here is an image: http://img2.timeinc.net/health/images/slides/hindu-squat-400x400.jpg
They LOOK unsafe to me, but mainly because my knees are wobbly after years of skating and other unsafe non-alignment based activities.

DancerFutureDPT, I'm really curious as to what your friend says about demi-plies. Perhaps the turnout keeps the pressure in the hips / glutes rather than knees? I'd love to know the reason, though I still feel uneasy about them. They violate everything I was ever told to do while squatting(namely keep knees well behind toes and bend the upper torso at the hips)

 

[DancerFutureDPT]

DancerFutureDPT, I'm really curious as to what your friend says about demi-plies. Perhaps the turnout keeps the pressure in the hips / glutes rather than knees? I'd love to know the reason, though I still feel uneasy about them. They violate everything I was ever told to do while squatting(namely keep knees well behind toes and bend the upper torso at the hips)

Alrighty, I talked to my friend today who is a dance teacher/dancer/PT. She said it's definitely not ideal, but by using the rotation and thinking of dropping/sitting straight down, which keeps the weight to the back instead of forward, that helps relieve some pressure and makes it slightly more acceptable. The knees should never roll in/go in front of the second toe to the front, but it will occasionally go past the toes sideways. Grand plies are better in first because the heel lift relieves pressure as well. And in second position the knees should never really go past the toes.