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ACL and Related Knee Injuries.....Shaped Skis Vs Straight Skis

Poll Results: Which cause more ACL and Knee related injuries Shaped Skis or Straight Skis

 
  • 50% (9)
    Shape Skis cause more.
  • 50% (9)
    Straight Skis cause more.
18 Total Votes  
post #1 of 192
Thread Starter 

I know there is a lot of interest in bindings for protection of these injuries (Knee Bindings being one of the most recent).  Before looking at the binding what is the cause and could it be the ski (ski shape in particular).

 

One of the things that I have noticed is that since stepping from straight skis to shaped skis this year (2012), there does seem to be additional loading placed on the knees.  Upon review of some of the old videos and new videos (with injuries) this does appear to also hold true.  It appears the shaped ski allow for more forces to applied to the snow vs the old straight skis of yester year.

 

This leads to the question, do shaped skis (while making the turns easier for the skier) actual increase the risk of injury to the knees as a direct result?

 

This questions is not intended to ask which binding is the best, but more so to possible help identify if shape skis might be part of the problem (BTW now that I have a set, you'll have to pry them from my cold dead fingers).  If this is the case it might be possible to help correct part of the issue if it is.  Solution I don't know, at this point I leave that to wiser minds.

 

Please have at it and provide your best opinions as I am doing this only for curiosity sake. For sake of making it easier Park skiing is not included (as I suspect that no matter  the ski, you are going to run the same risk for injury).

post #2 of 192

If you're looking for a ski technology rant look more at how many more people dart in to the woods and die after catching a shaped ski edge than occurred when everyone was using straight skis.  Hook a shaped edge and your momentary out of control direction radically changes whereas hooking a straight ski edge keeps you going straight but locked.

 

Still, I'll accept the additional risks in return for the ease of skiing on newer skis.

post #3 of 192
Thread Starter 

Thanks.  This wasn't intend to start a rant one way or another.  It was more of a question re possible cause of injury.

 

Was more trying to take the binding issue out of the cause and see if it could be ski related.

 

BTW I'll keep my shaped skis too biggrin.gif.

post #4 of 192
Quote:
Originally Posted by oldschoolskier View Post

Thanks.  This wasn't intend to start a rant one way or another.  It was more of a question re possible cause of injury.

 

Have a close look at rick howell's posts on this forum, specifically the range of distances from the heel he has isolated as being of interest.    

post #5 of 192
Thread Starter 

Thanks cantunamunch,

 

Occasionally the question as phrased in not found in the search engine.  Hence my post.

 

I have asked a similar question in one of the Kneebinding threads and no response (but then the thread was about the Kneebinding).

 

As to Rick Howell's comments re Bindings and upwards toe release, Tyrolia had a sort of system in their 390's did a slight "detensioning" for lack of a better word on the toe DIN in a rewards twisting fall.  The Marker M48 with the BIOMETRIC system did the same thing.  The M48's if you used to sit back and hang on your toes would always pop you as soon as your had any twisting loading.  It was not uncommon to crank up the toe at least 3 or 4 DIN points just to stay in.  I know as I skied a set from the early 90's to Jan 2012.  I was trying to avoid this portion of the equation in the thread (I leave that to potential solutions).

 

Honestly, don't know if the bindings are the total solution.

 

All this said, I currently use PX15's because of the way the toe pivots, I personally found the PX14's similar in release to the M48 just not as bad, hence the switch after only 2 days on them (second issue was the toe wings are plastic and I've had a plastic binding fail as a youth).

 

 

All of my skis in the last 30 years have been race skis with the most recent (2012) being a shaped ski.  The biggest difference I find (other than the shape) is the torsional stiffness and lack of feathering as you push the ski to the limits.  I've skied my wife's skis (High end SL type cut) and can say the same about those.  I've demoed a few intermediate/advance skis this year and other than too soft (for my preference), however they are torsionally stiffer than my old straight race skis.  Interesting experience, intermittent momentary control as the ski was pushed beyond the limits vs a softer let off and some chatter on the straight skis.

 

I am wondering if this torsional stiffness along with the shape of the ski is a contributor to the injury problem.   I was trying to keep the thread on the simpler side but I guess that's not going to happen.

 

Getting older (hopefully a little smarter) and looking for the right answers.  The saying I've always lived by is if you don't like the answer you shouldn't have asked the question.  I've asked and I gotta live by your honest answers. smile.gif

 

I think cdgildart hit it on the head with his comment "Hook a shaped edge and your momentary out of control direction radically changes whereas hooking a straight ski edge keeps you going straight but locked."

post #6 of 192

USSA and FIS are using increased ACL injuries as a rationale for dialing sidecuts back to higher radius year after year.  It's now looking to be 35 next year, up from 21 a few years back for GS.

post #7 of 192

Not sure how accurate these are but they are certainly on point-

 

http://www.ski-injury.com/specific-sports/alpine

The rate of serious knee sprains (in particular anterior cruciate ligament - ACL - sprains) initially jumped by some 240% (from the 1970's to the early 1990's), then remained static for about ten seasons with an ACL injury incidence rate in MDBI of about 2200. Since about the year 2000, the ACL injury rate has begun to decline. The next paragraph explains...

 

and

http://www.ski-injury.com/specific-injuries/knee

The introduction of carving (“super sidecut”) skis, which possess improved turning characteristics compared to traditional skis, was initially linked to an increase in knee injury rates. This was indeed seen in some of the alpine racing teams when they first started using carving skis in the early 1990's. This risk of injury with carving skis now seems to have diminished and in fact for the last 5 years or more the injury stats show that carving skis in fact protect against injury - the hypothesis is that established skiers who changed from traditional 'skinny' skis have now got used to carving skis and their improved carving characteristics.

 

and here is an Ortho`s take http://www.drstaub.com/ski.html

 The ligaments along the inside of the knee are 
injured when a skier catches the inner edge of a ski in the snow and the foot rotates outward as the 
body continues forward.  Stress is then placed on the inner side of the knee, which is forced into a 
“knock-knee” position as the skier falls.  The ligament will be stretched (sprained) if the force is 
minimal and if the bindings release.  Otherwise, the ligament can be completely torn...

 

The new shorter, shaped skis place more stress on the knees than the former, longer skis.

Especially stress on the medial collateral ligament  (MCL).

Prevention of these injuries mainly centers around adequate bindings.  It has been reported that a 
high percentage of lower extremity injuries result from a failure of bindings to release.  Quality 
bindings properly mounted and maintained will prevent many knee injuries.  Various knee braces can 
also be worn and, to some extent, can provide protection.  A brace with metal sidings and hinges can 
comfortably be worn under ski pants and allow an acceptable degree of knee mobility

post #8 of 192
Shaped skis tend to be shorter. Shorter skis put less torque on the knees - shorter lever arm physics. (Also they can be lighter.) Shaped skis also improve the skills of a skier - hopefully a skilled skier will fall less. Perhaps high level skiers may be able to push the envelope further and sustain more severe injuries, the paranoid race powers seem to think so.
For me, they seem to help as I have not hurt my knees since switching to shaped skis - despite an appetite for bumps and serious graying.
Eric
post #9 of 192

Shaped skis are beautiful performers — and here to stay:  however, the facts, both biomechanically and epidemologically are as follows:

 

Basic physics of Isaac Newton show that when T = f x d  and when properly functioning bindings supply a 'torque-limit', a long ski will produce the same torque about the tibia as a short ski (again, only when a limit is supplied by a binding), until — in the presence of the human anatomy — were the lateral force applied to the ski becomes incrementally closer and closer to the projected axis of the tibia — then the lateral force 'transforms' to produce more of a lateral shear-force ( in orthopedic terms, this means more of an 'abduction force' applied at the distal end of the tibia )  that is generating more valgus torque (about the femur) than torque about the tibia, when knee flexion is approximately 80 to 110-degrees (excluded angle).  Large valgus torque takes the ACL (and the MCL) directly past their elastic limit (the limit for a 50th-percentile male is ~400 Newtons of abduction-force applied to the ski ~15cm aft of the projected axis of the tibia = ~ 25 daNm of valgus torque).  Under the same loading conditions — where the lateral force that's applied to the medial edge of the ski operates under the same 'limit-conditions' of a properly functioning ordinary binding — and when the abduction force becomes applied incrementally closer and closer to the tibia, torque about the tibia approaches zero (the limit of a properly functioning 'ordinary' binding becomes irrelevant).  This is all basic physics-101.   These facts are proven both mathematically and experimentally by actual physical measurements.   So far, I am the only one on the planet measuring (experimentally) torque about the tibia and valgus torque as a function of the position of the applied force on the ski:  once others start to measure these interactions, everyone's light bulbs will go on. 

 

The experimental measurements produce clear results that dramatically prove how the forces supplied by longer skis that can 'slide-out' at either the tip (or, alternatively, at the tail) produce a single force that acts over the length of the ski to generate torque about the tibia, which torque about the tibia is limited by a properly functioning 'ordinary' binding (the resultant load on the tibia is crystal clear);  AND we also see, that experimental measurements produce results that dramatically illuminate how the two forces supplied at BOTH THE TIP AND THE TAIL by shorter-shaped skis (neither the tip or the tail slide-out when edged) produce a SINGLE RESULTANT CENTROID located under ( or near ) the projected axis of the tibia, where this singular loading-condition ( in orthopaedic termonology this is an 'abduction force' ) generates torque about the tibia that is well BELOW the limit supplied by a properly functioning 'ordinary' binding ( tibia torque approaches zero ) BUT WHICH ABDUCTION FORCE BECOMES TRANSFORMATIVE TO ACT OVER THE LENGTH OF THE TIBIA to produce massive valgus torque about the femur when knee flexion is large ( as during Phantom Foot and Slip-Catch events ).   This above loading scenario matches the most prevalent load-events, on-snow (Phantom Foot and Slip-Catch events) which are believed by leading epidemiologists to be associated with ~ 70% to 80% of all (prevalence) of skiing ACL injuries.

 

(( When the quantity of the applied load is BELOW the limit supplied by a binding, no release occurs:   When T = f x d and d =0, T = 0. ))

 

(( Straight backward loading ( as in "BIAD" events  — "Boot Induced Anterior Drawer loading events ) — where the anterior drawer component of the load-event is greater than the valgus torque produced by Phantom Foot or Slip-Catch events — appear to be present in approximately 15% of all skiing ACL injuries. ))

 

In addition to the plausible biomechanical / experimental measurements produced in the lab ( above ) regarding the dominant injury-mechanism (Phantom Foot or Slip-Catch events), epidemiological data consistently show that the incidence of ACL injuries (yes, that's expressed as mean-days-between-injuries) were very, very low when proper evidence-based data was first collected by the leading epidemiologists starting in the mid-seventies, then steadily and significantly rose during the eighties, plateauing during he nineties, and has only very, very slightly tapered-off since the mid-nineties.  The epidemiological data clearly also show that ACL injuries are BY FAR the most prevalent ( expressed as "% of all" ) type of skiing injury, today.

 

Binding toe pieces with upward release play no ( ZERO ) role in mitigating Phantom Foot or Slip-Catch events ( again, which PF and S-C events have a prevalence of ~70% to 80% of all ACL skiing injuries ):  bindings with upward toe release do directly effect BIAD events ( which BIAD events have a prevalence of ~10 to 15% of all ).  

 

On the other hand, bindings that have a release mechanism positioned along the kinematic pathway between the snow surface where load-events produce SINGLE RESULTANT CENTROIDS that enter the ski under (or near) the projected axis of the tibia — and the hip — (between the snow surface located under the projected axis of the tibia and the hip) — serve to limit the abduction forces that become transformed from producing torque-about-the-tibia to becoming valgus torque (torque-about-the-femur) — which bindings with special release mechanisms that are placed between the snow surface under the tibia and the hip directly effect Phantom Foot and Slip-Catch events (again, which events appear to have a prevalence of ~ 70% to 80% of all skiing ACL injuries).

 

The intersection of plausible biomechanical modeling (experimental measurements both in-computo and in the physical lab) coupled together with proper epidemiological data provide the proof.   There is much talk — but very few ( if, any ) measurements by those who can make a positive impact toward solving this problem.  Anyone ( 'well ... almost anyone ) who would like to observe these measurements are welcome to visit my lab here in Stowe, VT.   This work was also presented at the following ISSS (International Society for Skiing Safety) conferences:   ISSS-Switzerland, 2003:   ISSS-Japan, 2005;  and ISSS-Scotland, 2007.   At the ISSS-Germany, 2009 conference, the work was not presented but was published in the abstract before the conference.   The abstracts of the work from '05, '07 and '09 are available, publicly, and can be sourced through ISSS (this work was not published by the 'Journal of ASTM International' because I don't write papers, I make bindings) and can also be sourced through the peer-reviewed  Journal of Knee Surgery, Arthroscopy and Sports Traumatology.  The work from '03 can be purchased from the peer-reviewed journal of  Medicine & Science in Sports & Exercise  [St. Onge, N., Chevalier, Y., Hagemeister, N., Van de Putte, M., De Guise, J., “Effect of Ski Binding Parameters on Knee Biomechanics: A Three-Dimensional Computational Study,” Vol. 36, No. 7, pp 1218-1225, May, 2004].  More of this work will be presented at ISSS-Argentina, 2013.

 

There is only one non-pre-releasing binding that provides a mechanism that resides within the kinematic pathway between the snow surface and the hip which reads and reacts to the single abduction force that becomes transformed from producing torque-about-the-tibia (where a single abduction-force enters the ski NOT under or near the projected axis of the tibia — as can typically occur with a long straight ski) to becoming a producer of valgus torque (where the abduction force enters the ski as a SINGLE RESULTANT CENTROID under or near the projected axis of the tibia — as can typically occur with a shorter, shaped ski).  Anyone can engineer a binding to release in any mode:  not everyone can engineer a binding to release in a special mode that does not cause pre-release.  Here, my 'lab' is a result of my experience racing DH for many years at a high level on incrementally-improved experimental bindings that do not pre-release (independently of the settings);  from proprietary pendulum (dynamic impact) test methods since 1976;  and from the on-snow lab here on the mountain in Stowe, Vermont.   There is only one binding with this special mode of release that does not pre-release.   (( Mitigating pre-release is a higher priority than release (in a binding that is intended to release) because mitigating injuries that can be caused by pre-release ( head and spinal cord injuries ) is FAR more important than mitigating broken bones and ruptured or sprained ligaments. ))

 

Shorter shaped skis cause this transformation ( from producing tibia torque to valgus torque ) — and bindings that are utilized on shorter shaped skis must therefore apply the concepts of evolutionary biology (specifically, 'adaptive radiation') to deal with the transformitive-changes that are caused by our beautifully-functioning shorter shaped skis.   Bindings that can do this allow us to have it both ways:  easily carved-turns + lesser ACL injuries.

 

Rick Howell, Stowe, Vermont


Edited by Richard Howell - 5/16/12 at 4:37am
post #10 of 192

* ...of course, one would be remiss to not add that all alpine ski-bindings that are "intended to release" MUST also meet (1) minimum international alpine ski-binding standards ISO 9462, 9456 and 11087 (and their sub-standards);  AND  (2) must also meet  de facto  'standard industry practice'  for anti-pre-release and durability.   The term 'must' applies to  de facto  American case law;  to statutory German law;  and to enforcement actions in Switzerland by the BfÜ (Bureau for the Prevention of Injuries, based in Bern, Switzerland) who remove alpine ski-bindings from retail stores that do not gain approval from TÜV according to the ISO standards ( because Switzerland has learned that skiing injuries notably impact the Swiss-GDP ).   There is presently only one independent testing lab in the world that tests alpine ski-bindings according to the ISO standards (International Standards Organization — ISO is based in Geneva, Switzerland)  — and that independent lab is TÜV (based in Munich, Germany).   The ISO ski-binding standards are developed by 'consensus' from delegates representing DIN (Germany),  ASTM (USA),  AfNOR (France)  and  Ö-Norms (Austria).     'Standard industry practice' is  de facto  among binding manufacturers — and is the high-engineering-bar of field testing that forms a  de facto  economic barrier-to-entry, resulting in only a handful of alpine ski-binding manufacturers that can cash-flow operations past this key hurtle of anti-prerelease and durability, pre-revenue.

 

   :)  :)

 

Rick Howell, Stowe, Vermont
 

post #11 of 192
Thread Starter 
Quote:
Originally Posted by eleeski View Post

Shaped skis tend to be shorter. Shorter skis put less torque on the knees - shorter lever arm physics. (Also they can be lighter.) Shaped skis also improve the skills of a skier - hopefully a skilled skier will fall less. Perhaps high level skiers may be able to push the envelope further and sustain more severe injuries, the paranoid race powers seem to think so.
For me, they seem to help as I have not hurt my knees since switching to shaped skis - despite an appetite for bumps and serious graying.
Eric

Hi Eric,

 

Mathematically speaking it would appear so, however, the shape of the ski and the torsional stiffness add some other factors.  There is a good thread that talks a little about skiers ability http://www.epicski.com/forum/newestpost/112048.   Shape skis do not improve the skills of the skier, only the skier can do that smile.gif.  The apparent skill of the skier does go up in level because of the ease of turning, this is more evident in the lower levels when one switched from straight to shaped (I have some video (somewhere) of my wife making the switch and its as if she got in about 10 to 20 days, all it was was new skis and boots).  Unfortunately this false sense of ability does lead to avoidable crashes as not all skills are learn for the apparent level.  Just from your comment you are likely in the advance levels and its just renewed your youth so to speak biggrin.gif with the ease in which they turn.

 

Hi Rick,

 

I've read your other posts very interesting.  (I also remember when the Tibia measurement was part of the equation to determine the DIN settings, wish I had kept those instructions).  My background is engineering and this question is more of interest issue based on my limited experience with the shaped skis. I think that (mathematics aside) the shaped skis are torsionally stiffer which is also why the skis work the way they do with the side cuts.  Looking at other sports (IE windsurfing, primarily sail shapes), the biggest development has been how the power of the sail is feathered on and off by the design of the sail.  Applying this concept to the shaped ski, this feathering of power does not occur are readily as it used to compared to straight skis.  Example:  Straight Race Skis when overloaded just started turn slightly less as the tips and tails started to feather (twist off the load),  New Shaped Race Skis, not on your life....you can cut railway tracks on ice biggrin.gif.  Having skied a few intermediate/advance skis again the ski cut ice, the depowering occurres as chatter (up and down tip and tail movement) in turns resulting in abrupt power transitions vs feathers which just lets off easier.  I would attribute this to Torsion vs longitudinal stiffness.

 

I'm pretty sure that the correct binding design will help, the ultimate question remains what can be done with the ski design that we have the best of both worlds, allow some feathering and still have railway track performance.

 

Quick note on bindings: Marker M48's, the design of the Biometric to was very neat.  When loaded normally, the toe had a very normal release pattern.  However when a load was applied to lift the toe, this dropped of dramatically.  This could be easily demonstrated by pulling back on the cuff and applying slight pressure to the toe.  Talk about prerelease nightmares until you got used to changing your technique if you could (I had to, couldn't change skis just because the bindings caused problems so I adapted, but until I did, I had cranked the DINs to max on the toe just to stay in....oh those jet skiing days in bumps)

 

Back to skis....Interest how others view the risk. 

 

BTW I'm not going to vote myself as I do have a bias wink.gif


Edited by oldschoolskier - 5/16/12 at 5:53am
post #12 of 192

Does anyone want to 'vote' against Isaac Newton ?
 

post #13 of 192
Thread Starter 

Not me, I'm scared what ever hits me in the head will be bigger than an apple eek.gif


Edited by oldschoolskier - 5/16/12 at 6:03am
post #14 of 192

... re the ref to 'the DIN standard' — there are thousands of DIN (German Industrial Standards) standards — but by your ref, you probably mean DIN 7881, which was adapted (with some changes) to become ISO 8061 (Selection of Release Torque Values).  This standard can be purchased by anyone through ANSI (American National Standards Institute) and therefore, this standard is 'still available for you'. 

 

However, pls note that the standards I reference (above), ISO 9462, 9465 and 11087 relate to ski-binding design for binding manufacturers, not to the selection of release torque values for ski-retailers and for skiers.  However, all of these standards, including not only ISO 8061 but also ISO 9462, 9465 and 11087 can be purchased by anyone through ANSI, on-line.
 

(( Of course, there is no binding manufacturer standard ( yet ) that applies to the measurement of valgus torque — because the keepers of the flame still only observe bindings with their proverbial magnifying glasses (measuring tibia torque) rather than with telescopes (measuring valgus torque):  until others begin measuring valgus torque, the effects of 'shorter' shaped skis ('shorter' than older traditional long straight skis) will cause ACL injuries.  The classic required reading book for freshmen engineers at MIT,  Structure of Scientific Revolution,  by Thomas Kuhn, discusses this problem about those who hold the old-paradigm and who refuse to re-think in new ways.  The solutions to this problem ( the "Not Invented Here Syndrome") are not for the feint hearted ( I will not spoil the story for you ) ... but meanwhile, the people who are the 'old-guard' / keepers of the flame (who, ironically, are the same people today that were the 'radicals' that helped all of us skiers by solving the tibia-fracture problem back in the late 1960's and early 1770's) are the root of why we (as an industry) cannot break out of the skiing-ACL problem to run with the new flag (bindings that respond to valgus torque) to solve the knee-friendly problem.   (( Also of course, anyone can purchase a pair of these new bindings that respond to valgus torque at retail, then utilize a simple fish-scale to measure the new mode of release force as a function of setting indicator number to derive the selected release force (not valgus torque) values ... though that measurement (alone) will not, directly, illuminate the effects of the valgus torque relative to strain across the ACL:  measurement of femur torque directly correlates to valgus torque, especially when different length 'tibias' and different knee-flexion angles are introduced. ))  ))

 

:)   :)


Edited by Richard Howell - 5/16/12 at 6:27am
post #15 of 192
Quote:
Originally Posted by MEfree30 View Post


http://www.ski-injury.com/specific-injuries/knee

 This risk of injury with carving skis now seems to have diminished and in fact for the last 5 years or more the injury stats show that carving skis in fact protect against injury - the hypothesis is that established skiers who changed from traditional 'skinny' skis have now got used to carving skis and their improved carving characteristics.

 

 

It is also could be that the average carving and racing ski sidecut depth has decreased some along with the average turning radius increasing some over the past 5 years.  We're not seeing as many people on skis under 17r.  GS racers are now up above 29.  Powder and back country skis are also way up there.  I would assert that the decrease in injuries over the past 5-8 years correlates with the increase in fat powder ski and higher radius GS and carving skis quite well.

post #16 of 192
Quote:
Originally Posted by Richard Howell View Post

Does anyone want to 'vote' against Isaac Newton ?
 


The Vatican..  hahahaha

post #17 of 192

This is what happened to me but it was the outside edge of the inside foot (turning left to right) 

Quote:
Originally Posted by MEfree30 View Post

and here is an Ortho`s take http://www.drstaub.com/ski.html

 The ligaments along the inside of the knee are 
injured when a skier catches the inner edge of a ski in the snow and the foot rotates outward as the 
body continues forward.  Stress is then placed on the inner side of the knee, which is forced into a 
“knock-knee” position as the skier falls.  The ligament will be stretched (sprained) if the force is 
minimal and if the bindings release.  Otherwise, the ligament can be completely torn...

 

 

post #18 of 192

The above ref to ACL injuries is incorrect:  the facts show that, longitudinally over time, the rate of change of the incidence of ACL injuries is decreasing slightly, but that the actual incidence remains BY FAR the worst of all skiing injuries and that skiing ACL-injuries also remain the highest in terms of prevalence.  'Safety' ( I don't like that term ) is also measured both as a function of frequency and severity:  by this index also, skiing ACL-injuries remain EVEN MORE BY FAR the leading injury-problem in skiing, today.  BY FAR.  There is only one study that attempts to find that shaped skis do not correlate to skiing ACL-injuries — and that study was funded by Austrian ski manufacturers, and it does not properly (statistically) compare injured skiers to control-skiers (the sample sizes are too small and the p-values are not good).  Virtually all other studies, especially including the repeatedly-proven epidemiological studies by Johnson, Shealy and Ettlinger ( which are randomized, double-blind, evidence-based studies with statistically-valid sample sizes that compare injured populations and their equipment factors to  a control-population and their equipment factors and where diagnosis is conducted by on-site MD's (and where both the injured and the control pop's are 'closed' — meaning that very few skiers 'escape undetected by this study' to a 3rd-party clinic, hospital, etc.) , show, conclusively, that skiing-ACL injuries are BY FAR the most frequent in terms of both incidence and prevalence, TODAY, BY FAR.
 

post #19 of 192

The above discussion of individual (singular) events have been repeatedly proven to be unreliable in several extensively-researched studies spanning over 40-years where injured skiers who were videotaped were asked to describe their injuries (before they saw their injury-mechanism), then upon review of the videotapes, the actual injury-mechanism was typically VERY DIFFERENT from the injury-mechanism perceived by the injured skier. 

 

We must rely upon statistically-valid sample sizes of injured skiers compared to control-populations of skiers within properly conducted evidence-based research to properly point to trends in injury-mechanisms ... then utilize that information to construct plausible biomechanical models either 'in-computo' or with 'physical lab measurements' to simulate the injury-mechanisms that are discovered through the properly conducted evidence-based research.

 

That is all I'm going to offer at this time ( no more posts for a while ) ... because I must deal with other critical issues that are on my immediate horizon, which issues, if properly resolved, will help all of us move-forward with knee-friendly skiing.

post #20 of 192
Einstein successfully campaigned against Newton. Irrelevant here.

My two serious injuries would never happen with modern equipment. Boottop fracture from horribly designed antique Nordica red racer boots (I still carry a prejudice against Nordica products). Twisted out of one binding on a helicopter, rode out on one ski until the safety strap gacked my knee when the trailing wedged in a bump. Modern technology has completely removed these risks. Thanks!

I'm not sure I understand the issue. Does a knee injury usually happen at the first slip and twist? Or does the injury happen during the tomahawk? High level racers who can't make a turn because the ski's turn radius is too big would appear to be at a much higher risk of injury.

With a skiing population that is getting older and fatter, any reduction in injury rate is a huge endorsement of the safety of modern equipment. Do wall sits and quad tighteners to really protect your knees.

Eric
post #21 of 192
Quote:
Originally Posted by eleeski View Post
 High level racers who can't make a turn because the ski's turn radius is too big would appear to be at a much higher risk of injury.

Eric

What happens is that they transfer a lot more g-forces to the knees because the CAN turn tighter at higher speeds.  When they're skidding, pivoting, and chattering the energy gets dispersed.  When the skis rail and hold in the tighter arc at very high speeds a lot more force is exerted on the knees.. and the knee goes POP!

post #22 of 192
So the knee fails causing the fall? Seriously you want me to believe that?

I did abandon a project to make padded underwear for old people because the orthopod figured enough hip fracture falls happened because the hip fracture preceded the fall. The liability was too high because of that. But our targets were not conditioned athletes.

Avoid the fall, avoid the injury on skis.

Eric
post #23 of 192
Quote:
Originally Posted by eleeski View Post

So the knee fails causing the fall? Seriously you want me to believe that?
I did abandon a project to make padded underwear for old people because the orthopod figured enough hip fracture falls happened because the hip fracture preceded the fall. The liability was too high because of that. But our targets were not conditioned athletes.
Avoid the fall, avoid the injury on skis.
Eric


It is more that the ability to go faster and ski courses at higher rates of speed results in more injuries.  Slip CATCH eek.gifPOP is more the cause than hold hold popped knee.  They're dialing back to older sidecuts to slow down the skiers and reduce both the g forces and the likelyhood of crashes.  Make the skis too good and people get hurt on them pushing themselves beyond their physical limits

 

Quote:

 

FIS ISS identifies strategies to reduce ACL injuries

 

Alpine Skiing male athletes have been shown as having an increased risk compared to females and that the injury rate increases with increasing speed.

post #24 of 192
OK, better skis let you go faster and the injury risk goes up with speed. But the proposed rules confuse me. NASCAR puts restrictor plates in the engine not limits on the steering wheel. Perhaps outlawing flouro wax is more appropriate than requiring skis that don't turn

I borrowed super G skis for a masters GS race. I am not a great racer so I was challenged by the course anyway. I did OK time wise but was very uncomfortable and felt more at risk for blowing out of the course. I would struggle with the new rules. But I don't race much so the serious racers will adapt and enjoy.

Eric
post #25 of 192

Typo correction:   The elastic limit of the ACL is approached at 600 N ( not 400 N ) when an abduction force is applied to the medial edge of the ski ~15 cm aft of the projected axis of the tibia:  it is at this point ( ~ 15 cm ) where the resultant of mostly valgus torque is vector-added to a small amount of tibia torque to produce maximal resultant valgus-tibial torque at 24 daNm ( not 25 daNm ).   Thank you for your attention to this correction.  :)   :)

 

Rick Howell, Stowe, Vermont

post #26 of 192
Thread Starter 
Quote:
Originally Posted by eleeski View Post

OK, better skis let you go faster and the injury risk goes up with speed. But the proposed rules confuse me. NASCAR puts restrictor plates in the engine not limits on the steering wheel. Perhaps outlawing flouro wax is more appropriate than requiring skis that don't turn
I borrowed super G skis for a masters GS race. I am not a great racer so I was challenged by the course anyway. I did OK time wise but was very uncomfortable and felt more at risk for blowing out of the course. I would struggle with the new rules. But I don't race much so the serious racers will adapt and enjoy.
Eric

Eric,

 

I switch to Dynastar Speed Course WC GS 176's ski this year from Blizzard Thermo RS 205's, what a difference in G-Forces in turns and edge hold.  Both skis are GS race skis, but the difference in edging is unreal.  I could push past the limits of the Blizzards without problems (and I'm not a racer let alone a WC racer).  The Dynastars well I don't want to find the upper limit of the ski.  The feeling of cruising at 50 plus mph and accelerating at each turn regardless of the conditions.  Wow.  The additional loads on the knees, WOW!

 

Hence the question as I asked it. 

 

crgildart nailed it when he writes about the differences and why some of the changes are coming.  Look at old video of crashes, most the skiers slide out of the turns on straight skis, shaped skis, the skier is fired (like out of a canon) in strange directions by the ski.   I think for the most part the equipment far exceeds the abilities and strength of the human interface. wink.gif

post #27 of 192
OK, but for me, without the rush of speed and edge I won't race as much and when I do I will be quite timid. Injury issue solved but declining participants issue exacerbated. And the pros will push the limits no matter what.

Eric
post #28 of 192

wow

I'm glad to see that math and physic has a place here at Epicski.  Its to much for me.

 

My respones to Oldschoolskier  statement in the first post  "One of the things that I have noticed is that since stepping from straight skis to shaped skis this year (2012), there does seem to be additional loading placed on the knees."  I haven't had any increase loading on my knees and I have been the shape ski since Elan SCX's came on to the market. We do need to look at shape ski and binding but let's not forget the skier style ie the park and ride folks. I think that if you just drop inside the turn and the ski  hooks up on you will find that the knee will be taking a lot of abuse IMHO.

 

Hank 

post #29 of 192

Flawed pole.

 

Both styles of skis are equally likely to cause injury to knees, one is not more likely than the other.  Just my opinion.

 

BTW my old race skis are just as torsionally stiff as modern skisth_dunno-1[1].gif.

post #30 of 192

gravity kills.....

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