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Less Forward Lean = Higher Risk of Knee Injury?

post #1 of 29
Thread Starter 

If you ignore the boot flex and technique issues in order to get to the general principals at work, based on my admittedly limited knowledge and experience I believe that if you reduce the forward lean on your boots to provide a more upright stance it allows you to support your weight on your skeleton more and consequently you need to use your muscles less, and therefore can ski with less fatigue.

 

On the other hand, I believe that due to the physiology of the knee and the forces at work when skiing hard in various conditions and terrain that a more upright stance results in a substantially higher likelihood that you will injure your knees.

 

Bottom Line: A bent knee is more solid and stable than a straight knee, and the straighter it is the more susceptible it is to a twisting or hyperextension injury.

 

Acknowledging that the forward lean numbers manufacturers use are not comparable across brands (just like flex numbers), for me the noticeable reduction or increase in fatigue and stability is at about 15 degrees forward lean.

 

Anyone else have any information or insight on this issue?

 

 

 

Disclaimer: I am not a doctor, but I play one on TV.

post #2 of 29

it's more along the lines though of if you are a less "aggressive" skier, you can use a less athletic motion that matches the less forward lean and upright skiing.

 

If you are a more "aggressive" skier in a more athletic skiing, then the extra forward lean allows you to remain in that "aggressive" position.

 

Think of it more like bicycle riders. The casual family weekend department store bikers just sit upright and pedal away.  But any serious "biker" with their own road bike and the full getup has a completely different crouched biking position bent at the waist with their core tightened to support their weight.

 

So yea, basically you want to match the forward lean to the type of skiing you plan to be doing.  

If you are an upright skier with raceboots then it's a mismatch.  Same as if you're a racing skier with upright comfort boots.

 

Perhaps another analogy is just the way snowboarders setup their binding angles depending on the type of riding they will be doing.

 

I think the injury prevention is an unrelated side issue, as that is left primarily to your binding and DIN to pop off your skis when you are outside your envelope and bailing out.

post #3 of 29
Thread Starter 

raytseng:

 

I appreciate your comments and I do not dispute what you are saying, but my point is that injury is not an unrelated side issue.  The industry trend definitely seems to be boots with a more upright stance, which mirrors the modern ski designs which do not require as much forward pressure to initiate turns.   After years of skiing with a lot of forward lean (which works quite well for me) I started experimenting with a more upright stance.  After figuring out the required technique adjustments I found that it would work almost as well for all conditions, and my legs definitely felt less fatigued, but the feeling in my knees was noticeably less stable.  I felt closer to injury on a more regular basis, and I do not believe it was completely psychological.

 

Rockered skis definitely take twisting pressure off the knees, which compensates somewhat for the inability of your knees to withstand as much twisting when they are more extended, but I feel like there is a point where I have to make a choice between fatigue and safety.  I am just trying to find out if others have experienced this same thing, and where they draw the line on forward lean.

 

For the sake of the discussion I am assuming an expert skier that skis reasonably agressively all over the mountain.

post #4 of 29

I'm with you on this. No "gas pedal" position for me. I like having more forward lean built into the system.

Knees do not have much twisting strength at all with the unbent posture. And I believe more potenial for hyperextensions as well.

Just feel way more solid in an old school attack mode. biggrin.gif

post #5 of 29

I've gone through several boots with varying degrees of forward lean in an attempt to find a setup that works for me.

 

I could ski in all the boots I've been in, but from looking at videos of myself, it was apparent that I was contouring my body to remain in balance -- that is, I was fighting the position that my boots put me in.  I have finally found happiness with the Lange RS130's, which (to my understanding) is one of the most upright boots out there.

 

My point is that if you're in a boot that forces you to "balance" via some awkward body positioning, then I'd think your chance of injury goes up as your available range of motion is limited.  If your boot allows you to balance in a nice, relaxed stance, then your chance of injury goes down.  Depending on your body's geometry, the ideal forward lean of your boots will change.  For some people, that ideal forward lean will be substantial.  For me, it's minimal.

post #6 of 29
Quote:
Originally Posted by KevinF View Post

I've gone through several boots with varying degrees of forward lean in an attempt to find a setup that works for me.

 

I could ski in all the boots I've been in, but from looking at videos of myself, it was apparent that I was contouring my body to remain in balance -- that is, I was fighting the position that my boots put me in.  I have finally found happiness with the Lange RS130's, which (to my understanding) is one of the most upright boots out there.

 

My point is that if you're in a boot that forces you to "balance" via some awkward body positioning, then I'd think your chance of injury goes up as your available range of motion is limited.  If your boot allows you to balance in a nice, relaxed stance, then your chance of injury goes down.  Depending on your body's geometry, the ideal forward lean of your boots will change.  For some people, that ideal forward lean will be substantial.  For me, it's minimal.

 

 

I think the OP is really talking more about pure body mechanics here. Balance is one thing but if you are balanced in a less sound position, is that actually desirable?

post #7 of 29

Mudfoot,

 

If more forward lean = more fatigue, isn't a more fatigued person likely to injure themselves more easily.  On the other hand if a more upright stance

is more easily balanced (strength wise) wouldn't that in itself be safer?

 

Most ACL injuries occur with the leg flexed and the skier out of balance on the uphill ski.

 

mike

 

PS.  I don't think anyone can completely straighten the knee joint while in ski boots without getting way out over the front of their skis,

the idea is to have the upper leg (femur) oriented in a more perpendicular position over the ski center, using the skeleton to support the

G loads instead of the quads.


Edited by miketsc - 7/31/12 at 10:13am
post #8 of 29
Thread Starter 
Quote:
Originally Posted by miketsc View Post

Mudfoot,

 

If more forward lean = more fatigue, isn't a more fatigued person likely to injure themselves more easily.  On the other hand if a more upright stance

is more easily balanced (strength wise) wouldn't that in itself be safer?

 

Most ACL injuries occur with the leg flexed and the skier out of balance on the uphill ski.

 

mike

 

PS.  I don't think anyone can completely straighten the knee joint while in ski boots without getting way out over the front of their skis,

the idea is to have the upper leg (femur) oriented in a more perpendicular position over the ski center, using the skeleton to support the

G loads instead of the quads.

 

Could you please elaborate on your statement about how most ACL injuries occur.  I am no expert, but it is my understanding the it is much easier to injure your ACL, or almost any other part of your knee, when it is almost straight.  Most injuries occur due to falls, and most falls occur like you describe, but overall isn't it harder to injure you knee when it is flex?  Generally, you injure your ACL by being in the back seat, and that is probably more likely with less forward lean in your boot.

 

Regarding the fatigue factor, yes you are more likely to injure yourself when tired, but I think putting yourself in a more vulnerable position to be able to ski more vert without stopping kind of negates that.

post #9 of 29

 

 

You said it, Quote: "Generally, you injure your ACL by being in the back seat, "  Butt behind heels---often caused by knee being too far forward and skier sitting back.

 

Isn't this back seat position, "a bent knee position", it isn't a straight leg position.

 

mike

post #10 of 29
Thread Starter 

Miketsc:

 

So in your opinion, all other things being equal, is a guy more likely to injure his knees with 18 degrees of forward lean or 12 degrees of forward lean, or doesn't it make any difference?

 

MF

post #11 of 29
Someone with birdleg calves might ski ok with 18 degrees of forward lean,, on the other hand, if he had 15 in circumference calves in the top of the boot he
might be in agony.
Bigger calves equals more tibia net forward lean and the need to sit back more.

To answer your question
I doubt it would make a lot of difference since the leg is very seldom (read never) in a static position and any time while skiing.
I also stand by my comments about fatigue affecting safety, so I think you are better off in a more centered position, (femur nearly perpendicular to ski center).

Mike
Edited by miketsc - 7/31/12 at 5:23pm
post #12 of 29

To answer you question:

 

Conventional wisdom is almost all knee injuries occour when the knee is bent...as your knees bend gets over 90 degrees (ie hips below your knees) the chance of blowing your knees, goes way up.  Having said that, you can get in that positon with boots with little forward lean, and a lot...so I dont think it matters.  Certainly never ever heard of risk of injury with straight legs...just the opposite. 

 

If your knees feel unstable in the more upright boots, they probably are.  But I highly doubt its a function of the fore/aft balance point, it would be a function of your lateral alignment being out.  Fix that.  If common symptom of poor lateral alignment is your knees "wobble" in/out.


Edited by Skidude72 - 8/1/12 at 12:52am
post #13 of 29

I would agree that fatigue is overwhelmingly more important in causing injury than any difference in forward lean.  I took the rear spoilers out of my Rossi Radical Pros--a lot less fatigue skiing off piste and I'm happy to sacrifice groomer performance for that. Anything that makes skiing more comfortable has to be good (by which I mean comfortable skiing fast,skiing powder, skiing steep, skiing bumps, etc--not comfortable cruising blue groomers.) I think the OP is over thinking the issue. (Over thinking isn't so great for skiing either.)

post #14 of 29

Jasper Shiely at Vermont Safety Research found that most ACL sprains occurred when the skier was off-balance on his uphill ski, with the hips below the knees.  Most of the rest of the injuries occurred when the skier landed a jump off-balance to the back,with the legs straight.

The range of forward lean among boots can't be much more than 6 degrees.  That doesn't seem like enough to have any affect on those 2 injury mechanisms.

 

BK

post #15 of 29

^^^^  This brings up the issue of the straighter you are the more compressive force is transmitted to the spine/hips/knees.  It seems intuitive (and that's never wrong, right?) that there's a certain amount of optimal flex/forward weighting that will minimize the chance of compression injuries; it gets much more complicated with other injuries common to skiing, however.  I think we need to keep in mind the difference between boot flex and weight distribution - just because you have 18 degrees of forward lean doesn't necessarily guarantee that you will be in the best position to absorb compressive shock.  Something that doesn't get the attention that I think it deserves, perhaps because it's very difficult to analyze, is, instead of focusing almost entirely  on the position of the body when the injury occurs, instead go back and determine where was the body when things first started to go bad. Boot lean angle may aggravate injury conditions the final moment, but it may also contribute to setting up the skier for injury in the first place.  Fatigue and pain are obvious examples, but I think it's more complicated than that.

post #16 of 29
Thread Starter 
Quote:
Originally Posted by Bode Klammer View Post

Jasper Shiely at Vermont Safety Research found that most ACL sprains occurred when the skier was off-balance on his uphill ski, with the hips below the knees.  Most of the rest of the injuries occurred when the skier landed a jump off-balance to the back,with the legs straight.

The range of forward lean among boots can't be much more than 6 degrees.  That doesn't seem like enough to have any affect on those 2 injury mechanisms.

 

BK

 

The injury situations described are rookie mistakes caused by not having your weight forward enough and are endemic to the classic tail pushers.  Not surprisingly, bad skiers have more injuries, but I am talking about something different.  An expert skier in crud or bumps on a 18 or 12 degree forward lean boot can make either work, but with the 12 degree his neutral position will be more upright and legs will be straighter more of the time while skiing. My question is simply, from a physiological standpoint does spending more time more upright put the skier's knees in a more vulnerable position more of the time? 

 

It is obviously harder to balance when you are more upright in a dynamic situation because of your higher center of gravity, but am I wrong in thinking the mechanics of the knee leave it more susceptible to twisting forces the straighter your leg is?

post #17 of 29

Bode Klammer,

 

You are right about the variance in forward lean being about 6 degrees (mens boots), the problem comes in when you put different sets of legs (calf diameter) into those boots.

A 5 year old Salomon Falcon has about 18 degrees if we combine this with a leg with 18 inches of circumference calves, the net tibia forward lean can be huge.  This poor 

guy would have to sit back all of the time---his quads would be in agony until (if ever) he got his legs into good enough shape to hack the load.

Skiing under these conditions is a night mare to say the least, but we see if all the time.

 

Mudfoot, started off by commenting about more upright boots being detrimental to safety. Although the twisting forces are different the mechanical disadvantages 

of skiing in a squat, out weigh any problems associated with an upright stance.   All of the instructors are always chorusing "Stand Tall".  They definitely have reasons

for all of this.  Center of mass, fore/aft balance problems are controlled by ---boot board angle---binding differential heel to toe(delta angle)---forward lean of the boot---and calf circumference,

(these two are related), ultimately we need to get the skiers tibia into the correct position to allow the him to stand with his torso centered over the boot sole center and the femur carrying the load into the knee joint.  This allows the skier to use the thigh and trunk muscles to control position verses having to carry all the G loads and control position.

 

In order to absorb you have to be extend---if the knee is too far forward, extension will overload the shovel of the ski, the skier will then sit back a little and load the tails.redface.gif

mike

post #18 of 29
Quote:
Originally Posted by mudfoot View Post

The injury situations described are rookie mistakes caused by not having your weight forward enough and are endemic to the classic tail pushers.  Not surprisingly, bad skiers have more injuries, but I am talking about something different.  An expert skier in crud or bumps on a 18 or 12 degree forward lean boot can make either work, but with the 12 degree his neutral position will be more upright and legs will be straighter more of the time while skiing. My question is simply, from a physiological standpoint does spending more time more upright put the skier's knees in a more vulnerable position more of the time? 

It is obviously harder to balance when you are more upright in a dynamic situation because of your higher center of gravity, but am I wrong in thinking the mechanics of the knee leave it more susceptible to twisting forces the straighter your leg is?

There is really nothing correct in your post. Rookie mistakes? These are WC racers and pro free skiers studied along with general public. It's often massive compression forces that cause the skier to get the hips like that, takes certain skill to generate those forces in the first place.

The answer to your first question is "no". The answer to your second question is "Yes"
.
You need to also consider the other half of the twist, the ski is twisting, but something above the knee must be resisting that twist to cause the knee pop (or alternatively the ski is held firm and the twist is coming from the upper body moving....this is common too). Lay down on the bed and try it. Straight leg, you will notice that you leg can absorb twist in the Tibet/fib and hip....it can tkae a lot of twist easily. Now bend your leg so hips are below the knee and try again. You will note here the hip is locked, so only the tib/fib can twist which is not a lot, the knee has to do the rest, and with the ligaments tight from the flex, they now just snap.


In regards to you Second question, balance is dynamic, the greater your range of motion the easier it is. Straighter boots allow you to acess the upper range of your motion. Think of it like a mountain bike, 12inches of travel vs. 18inches. Which is easier to balance on at speed? You want more travel, not less....same with skiing, but your legs are the suspension system, more is better.


As I wrote earlier, I suspect your lateral alignment is way out creating your stability issues.
post #19 of 29

You start out talking about a tall stance seeming wobbly.

 

Now we are all curious----what boots are you in----what size boot---what size street shoe----has your lateral alignment been set up correctly---circumference of calf at top of boot?

 

mike

post #20 of 29
Thread Starter 

Skidude:

 

Thanks for your opinion, "The answer to your first question is "no" is really all I was looking for. There is nothing correct in your assumptions about the rest of my post, but I appreciate the comments.  MF

 

 

Mike:  I never said I felt "wobbly."  I have been fitted in every respect by an expert and do not have stability issues, and I have experienced the same feeling over the years when experimenting with the forward lean on two different alpine boots, two different telemark boots and two different AT boots.  If you are too crouched due to a lot of forced forward lean because of your boot set up then your quads have to support you and they never get a complete release. On the other end if your neutral position is too upright it is difficult to initiate pressuring the boot so there is a gap between standing on the ski in a relaxed postion and working the flex.  That gap seems to appear for me when skiing with boots at the >15 degree point.  I am concerned that the "gap" (for lack of a better word) seems to me to be a dangerous place for me knees to be in, and I was wondering if others experience the same feeling.  It is not a question of my knees being unstable but of them not being connected to anything solid, which I do not feel when skiing with more forward lean.  Booster Straps have not resolved the issue.

 

I ski better with more forward lean, but my legs get less fatigued when I'm upright. I am just trying to determine if skiing more upright increases the chance of a twisting knee injury (so I can better determine where do draw the forward lean line)  Apparently the anwser is "no," at least according to a few of you here. 


Edited by mudfoot - 8/1/12 at 1:52pm
post #21 of 29

Not that it really applies to this discussion, but I suffered a tibial plateau fracture while skiing last January due to hyperextension.  This was in a pair of Salomon Course boots that have a fair amount of forwar lean so if you put yourself in a crappy position (I was skiing backwards and pitched forward - not on purpose - and trying to avoid hitting a friend that had fallen in front of me), you can suffer a season endig injury due to hyperestension.  My recovery has been slower than hoped and I'm not sure I won't miss the first half of a second season...

post #22 of 29
Sticking to the OP, bc there are tons of great offshoots that all have merit on their own, I think the question is does forward lean cause injury?

My bias is that I believe we are giving the boot an excessive amount of credit. From my experience, the skier settles into a posture that works for them. Really the diffence from 15-19 degrees is only relevant when the boot is on the showroom shelf.

My stance is quite similar in tele, at, racers, flexons once I am out & turning. Even in a WC 160 plug that I gas pedaled my 10 mm (quite a dumb idea as I could do nothing w the tails...) I assumed my stance relative to the starting point. Even though I can't seem to ski my Fult Tilts / Flexons, w / o a big lean shim, it is only to get me to my 'normal' stance.

Don't forget, between boots & models, sole length, pivot points, stiffness & liners all vary quite a bit. Even in the same boot, if you change a liner or footbed you alter the starting geometry.
post #23 of 29

I'm more curious about your disclaimer?

post #24 of 29
Quote:
Originally Posted by 2meke View Post

I'm more curious about your disclaimer?


More details please.
post #25 of 29

After having had my knees abused for many decades in many dangerous sports, fights, and other unmentionable activities, I tend to agree with the basic premiss.  Knees are more easily injured when straight than when bent.  However, I have also found that if they are bent past 90 degrees, they once again become more susceptible to injury.  No studies, no proof, just my own decades of anecdotal information.

 

PS - regarding fatigue.  I can recall that often at the end of a long day a pair of very stiff forward leaning boots was all that was holding me up ;)

post #26 of 29
Thread Starter 

Quote:

Originally Posted by Ghost View Post

After having had my knees abused for many decades in many dangerous sports, fights, and other unmentionable activities, I tend to agree with the basic premise.  Knees are more easily injured when straight than when bent.  However, I have also found that if they are bent past 90 degrees, they once again become more susceptible to injury.  No studies, no proof, just my own decades of anecdotal information.

 

PS - regarding fatigue.  I can recall that often at the end of a long day a pair of very stiff forward leaning boots was all that was holding me up ;)

 

Thanks Ghost, your comments perfectly reflect my thoughts on the issue.  Assuming you don't spend much time skiing with your legs bent more than 90 degrees, the action is all happening with an forward lean angle of probably 25-10 degrees. Standing up straighter more of the time is definitely less stress on the leg muscles, but I believe there is a point where it adversely effects technique and increases the likelihood of injury, and I believe that point overlaps around the 15 degree mark.  A lot of forward lean may ski great, but in my advancing years I need to use my skeleton more and muscles less.I am just trying to figure out the spread between the max efficiency and danger of injury points.   ndhdhdI am just trying to figure out the spread between the max efficiency and danger of injury points. I am just trying to figure out the spread between the max efficiency and danger of injury points.                    I I   II          

 

I am just trying to figure out the spread between the max efficiency and danger of injury points.

post #27 of 29

A lot of forward lean does not necessarily ski great. Are you taking in to account ski's that are designed for a more centered stance?

post #28 of 29
Quote:
Originally Posted by mudfoot View Post

Quote:

Thanks Ghost, your comments perfectly reflect my thoughts on the issue.  Assuming you don't spend much time skiing with your legs bent more than 90 degrees, the action is all happening with an forward lean angle of probably 25-10 degrees. Standing up straighter more of the time is definitely less stress on the leg muscles, but I believe there is a point where it adversely effects technique and increases the likelihood of injury, and I believe that point overlaps around the 15 degree mark.  A lot of forward lean may ski great, but in my advancing years I need to use my skeleton more and muscles less.I am just trying to figure out the spread between the max efficiency and danger of injury points.   ndhdhdI am just trying to figure out the spread between the max efficiency and danger of injury points. I am just trying to figure out the spread between the max efficiency and danger of injury points.                    I I   II          


I am just trying to figure out the spread between the max efficiency and danger of injury points.


Actually some studies have found that a good deal of time is spent in the 80-110 ranges for GS skiers.....
post #29 of 29
Quote:
 
Quote:
Originally Posted by mudfoot View Post

Quote:

Thanks Ghost, your comments perfectly reflect my thoughts on the issue.  Assuming you don't spend much time skiing with your legs bent more than 90 degrees, the action is all happening with an forward lean angle of probably 25-10 degrees. Standing up straighter more of the time is definitely less stress on the leg muscles, but I believe there is a point where it adversely effects technique and increases the likelihood of injury, and I believe that point overlaps around the 15 degree mark.  A lot of forward lean may ski great, but in my advancing years I need to use my skeleton more and muscles less.I am just trying to figure out the spread between the max efficiency and danger of injury points.   ndhdhdI am just trying to figure out the spread between the max efficiency and danger of injury points. I am just trying to figure out the spread between the max efficiency and danger of injury points.                    I I   II          


I am just trying to figure out the spread between the max efficiency and danger of injury points.


 
Originally Posted by iriponsnow View Post


Actually some studies have found that a good deal of time is spent in the 80-110 ranges for GS skiers.....

 

 

Or steeps...

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