Skiing on fat skis. When are they too wide?

[fatbob]

Well, perhaps some science might convince you otherwise.

Yeah I've dipped into that before but I'm not sure the "science" there is saying that your knees are fooked if you happen to ski an outrageously wide 95mm ski. I acknowledge they are saying that highly competent skiers achieved more consistent and higher performance turns on a controlled groomer on a skinnier ski. And if get to the 1.16 mark we get to the heart of it that kids will develop with better skills if they ski SL skis all over the mountain in all conditions. Also probably indisputably true.

But we're not all kids, don't all have all the time in the world to build our skills and I don't know about you but when there is soft snow and its on my dime I wanna be having as much fun as I can. And weirdly my knees aren't as bad as when I was 12-15 years younger despite skiing on average fatter skis. An ACL recon and the associated gym time in rehab seems to have much reduced previous problems. Maybe I'm just on average also finding softer snow?

 

[SSSdave]

I'm not familiar with the many different skis though have been using a 3 or 4 ski quiver for the last decade. With soft snow conditions there is a limit to how wide a ski might be beneficial as a matter of weight and generated forces versus effective ski surface area to support such. As skis become wider with more surface area, in soft snow that also decreases snow resistance that increases speed and thus average forces to contend with. At some point, I personally dislike such higher speeds and prefer to regulate forces by efficiently dynamically turning more, reducing speed.

Additionally regarding being able to cope with wide skis without knee stress, our individual bodies have a great range of strengths and fitness depending on a range of factors including age. At extremes might be downhill racers versus novices that ski little. I'm a senior that skis rec moguls like twentysomethings and although I've had some minor knee issues at times like loose cartilage and collateral ligament strains over decades that self healed, my knees are still extraordinary. Thus much has to do with how each of us keep our bodies healthy and fit as well as genetics and more.

 

[ScottB]

I have a 101mm wide ski that will bother my knees and a 142mm wide powder ski that does not bother them. The 101 has a lot of side cut (15m radius) and hence 145 mm wide tips. The 142 has about a 30 m raidus and 161 wide tips. Wide tips and a skinny waist make a difference too. I only use the 142 on powder days, so in soft snow its no problem on the knees. I will use the 101 on hard pack and my knees let me know about it by the end of the day. I have narrower skis I am on most of the time. Wide skis have their use, but you need the right tool for the job approach for sure.

 

[Mike King]

Yeah I've dipped into that before but I'm not sure the "science" there is saying that your knees are fooked if you happen to ski an outrageously wide 95mm ski. I acknowledge they are saying that highly competent skiers achieved more consistent and higher performance turns on a controlled groomer on a skinnier ski. And if get to the 1.16 mark we get to the heart of it that kids will develop with better skills if they ski SL skis all over the mountain in all conditions. Also probably indisputably true.

But we're not all kids, don't all have all the time in the world to build our skills and I don't know about you but when there is soft snow and its on my dime I wanna be having as much fun as I can. And weirdly my knees aren't as bad as when I was 12-15 years younger despite skiing on average fatter skis. An ACL recon and the associated gym time in rehab seems to have much reduced previous problems. Maybe I'm just on average also finding softer snow?

What I pointed you to in the video was not performance, but the forces of a wider ski. There's about 10-15 minutes from the bookmark in the video above that discusses both the theory and the instrumented results. There's no doubt that wider skis exert more force on the knee -- that's simple physics. The rest of the story is that skiers ski with greater outside leg extension on wider skis -- on average, 14%. And at the point of maximum force in the turn, the knee is at a greater point of extension. Why does it matter? Because at that level of extension, the muscle strength to stabilize the knee is lower just due to biomechanics.

The data and theory shows that wider skis, on hard snow, exert both greater force and result in biomechanics accommodations that place the knee in a greater point of vulnerability. Voilla -- knee pain.

So, as @Doug Briggs said above: "Evaluate conditions, determine goals for the day, choose a ski."

 

[fatbob]

Yeah I get that but I don't know if greater vulnerability = greater knee damage. The human knee is a pretty amazing joint. Now clearly we can damage it and improve it with surrounding muscle strength.

If we took the wide skis screw your knees thesis to its logical conclusion then there would surely be more people who took up skiing in the past 20 years limping around because there is no doubt that average waist width is probably about 20mm wider than the previous 20 years. The problem with the thesis is that it is most enthusiastically adopted by those who also bang the "you can't be a good skier unless you're skiing deep powder on SL skis" gong and the "punters are hacks who skid turns" snobbery.

Sorry for being argumentative but it feels good to get into a minor difference of perspective as a distraction at the moment even if its a massive retread of old ground- maybe I'm perilously close to caring about skiing again

 

[cantunamunch]

If we took the wide skis screw your knees thesis to its logical conclusion then

...we should definitely look at knee issues amongst snowshoers.

 

[maverick2]

When ya planning on changing boots?

Boots are on the list for this next season. (Master plan was to do that this spring during end of year sales, but all that went by the wayside when travel shut down and my ability to try on boots went out the window...)

 

[Rod9301]

Yeah I get that but I don't know if greater vulnerability = greater knee damage. The human knee is a pretty amazing joint. Now clearly we can damage it and improve it with surrounding muscle strength.

If we took the wide skis screw your knees thesis to its logical conclusion then there would surely be more people who took up skiing in the past 20 years limping around because there is no doubt that average waist width is probably about 20mm wider than the previous 20 years. The problem with the thesis is that it is most enthusiastically adopted by those who also bang the "you can't be a good skier unless you're skiing deep powder on SL skis" gong and the "punters are hacks who skid turns" snobbery.

Sorry for being argumentative but it feels good to get into a minor difference of perspective as a distraction at the moment even if its a massive retread of old ground- maybe I'm perilously close to caring about skiing again

Yeah, i ski on a 112 mm ski all the time, no knee pain. I have arthritis under the patella, but the meniscus is in good shape, so maybe that's the issue.

 

[jseeski]

FWIW (not much), I use a 96mm M5 Mantra as my daily driver in a world where the snow is usually at least somewhat soft. When something awful has happened and the best skiing is on firm groomers, I bring out an old pair of 78mm K2s. When there is 8" or more fresh, I use 106mm Elan Ripsticks. All are 174-177cm long. I have also used a pair of 115mm skis when cat skiing, but I don't own that pair.

My boots are Nordica Dobermanns with custom liners, much punching and grinding, sole cant, etc.

I am 5'11", 165 lbs and am 68 years old.

I have not experienced any knee soreness that I can blame on the ski width - but as has been pointed out above, everyone is different.

My knees seem to be pretty good, but they're not bulletproof. Sometimes I get some minor pain in my left knee that I believe to be caused by personal technique issues, regardless of the width of ski I am using. If I correct the technique problem (i.e., improve my balance/stance) the pain fades, even while I am still skiing.

Note that anxiety over snow conditions, terrain, obstacles, etc. may cause some skiers (i.e., me) to drop their hips back a couple of inches. The quads pull on the knees to support the skier's weight. This can contribute to knee pain. If the skier is using a wide ski on hard snow, and thus generating greater forces at the knee than a narrower ski, dropping the hips will make it worse. The resulting pain adds to the anxiety and may create a negative feedback loop.

 

[Paul Lutes]

Well, perhaps some science might convince you otherwise.

So .....I was disappointed with the weak/almost non-existent explanation as to why increased stack height only makes it worse. Can anyone provide more specific details as to why this is so?

 

[migdriver]

The debate over the effects of riding a wide ski - do they make my knees hurt more etc - is interesting , but highly subjective depending on a lot of different variables. Here's what is not subjective: there are a growing number of controlled studies looking at the effects of wide skis on body movement with several interesting observations. Wide skis ( greeter than 95 or so underfoot, though definitions vary) change the kinematics of the knee when skiing. Knee cartilage and ligaments appear to be subjected to alteration of the forces they "see" during a turn compared to narrow skis, the tibia ( lower leg bone) and the femur ( thigh bone) move somewhat differently ( rotation) when on a fat ski relative to each other amongst other things. There is speculation that the change in femur on tibial rotation MIGHT increase the risk for tibial plateau. But it is just that: speculation.
Here's the problem: large studies to help nail this sort of stuff down (relative to injuries that do occur) are lacking because for the most part the data just isn't available. At my home hill ( where I recently did a multiyear retrospective look at instructor injuries) the bottom line is while ski patrol and others collect DIN settings, skier type etc for on hill injuries, there is no data collected on ski width/sidecut, length etc. And snow conditions when they are recorded are very subjective. I often joke that a "firm" or "hard snow" day here - a v large California resort - would often be a delightful packed powder day in mid-northern Vermont.
So, while there is agreement that wide skis do alter body mechanics there is considerable debate whether this changes the likelihood of injury. As to whether wide skis are more uncomfortable to ski...well, each of us probably already has a personal sense of that one way or the other.
Just as an observation, around here unless it's a pow day, the better skiers on the hill tend to be on a more modest 75-85 underfoot. And another data point: my understanding is the Extreme/Freeride Team here places a 96mm underfoot limit on what the athletes can ski. And these kids rip the whole mountain in all conditions.

 

[markojp]

Small beers stuff. If you're knees hurt, ski something narrower or just ski low edge angles. If you value accuracy, then narrower's the ticket.

 

[David Chaus]

Let's see if this helps.

I'm in the PNW, so keep in mind there is a lot of snow, and while not light, it's nonetheless softer than a lot of places. My daily driver is 90mm wide, and I'd be equally happy on something narrower for groomers/hard pack, bumps, etc. It's a wider carver, the geometry of that particular ski rewards tipping of the ski to engage the edges to initiate turns.

My other skis are 116mm wide. The shape and geometry are different than the 90's. It had a lot of early rise (rocker) in the tip and tail, and probably less effective edge than the 90's. They can carve, though that requires more effort and and more tipping at the feet and more lateral movement of my knees to get the edges to really engage. Not just sort-of engage, but to really feel the forces of the mountain pushing up against my gravity and centripetal forces. They are very surfy, and are really more suited to steering and pivoting. There is less need to focus on getting them on edge in hard pack, therefore I don't feel the stresses on my knees as if I used the same focus as on my 90's.

That said, I used them sparingly, maybe 3-4 times in the last season.

Both skis still require/reward all the skiing movements: tipping, steering, fore-aft balance, shifting weight to the outside (more with the 90's, less so with the 116's), just different emphasis.

 

[Mike King]

So .....I was disappointed with the weak/almost non-existent explanation as to why increased stack height only makes it worse. Can anyone provide more specific details as to why this is so?

More leverage at the knee. Archimedes lever.

 

[Brad J]

I am 65 years old , been doing carpentry since I was 14, skied since I was 6 and I am on knee management during the ski season. I have no ACL on left leg as well as a ruptured quad tendon that is repaired. so last year I skied 12 days out west in terrific conditions with new snow in 8 of those 12 days on my new 106 mm ski's. at the end of the second week I was limping , my right knee was really sore and couldn't do squats and got much worst after I got home. I healed up 90% over the summer with PT.. This year I skied the same conditions the first week on a pair of 95's and the second week on a combo 95 and 83mm in much firmer conditions with no increased knee pain , I am still dealing with the remaining 10% problems with that knee but they felt much better. I know my observations are by no means a study but I know how my body feels. My old knees feel good on very firm groomers and bumps on the 74's , eastern and western packed powder on the 83's and powder days on on the 95's. I ski about 40 days a year and every year is different but I could feel the difference in the stress I felt on the knee with the wider ski . I know I am closing in on my days with these knees and hopefully the replacements that I properly will have some day will provide me with lots of years left skiing but I will be leaning towards the narrower ski for the conditions every time.

 

[Johnny V.]

Small beers stuff. If you're knees hurt, ski something narrower or just ski low edge angles. If you value accuracy, then narrower's the ticket.

This is it..............just one old man's opinion, but trying to get high edge angles on firm/hard/very hard/pretty darn close to ice conditions with wide skis is not only hard on the knees, but fatiguing on the legs. I'll take something narrower in those conditions, thanks.

There are a couple of guys who are excellent skiers at our home mountain who ski wide (100+) skis all the time on eastern hardpack. BUT, they are not getting high edge angles nor are they trying to-just not their style.

 

[Paul Lutes]

More leverage at the knee. Archimedes lever.

I certainly see more leverage on the skis, but still unclear on more on the knees ...... perhaps in geezer terms? Where's the fulcrum?

 

[Mike King]

I certainly see more leverage on the skis, but still unclear on more on the knees ...... perhaps in geezer terms? Where's the fulcrum?

The edge.

 

[Jim Kenney]

I am 65 years old , been doing carpentry since I was 14, skied since I was 6 and I am on knee management during the ski season. I have no ACL on left leg as well as a ruptured quad tendon that is repaired. so last year I skied 12 days out west in terrific conditions with new snow in 8 of those 12 days on my new 106 mm ski's. at the end of the second week I was limping , my right knee was really sore and couldn't do squats and got much worst after I got home. I healed up 90% over the summer with PT.. This year I skied the same conditions the first week on a pair of 95's and the second week on a combo 95 and 83mm in much firmer conditions with no increased knee pain , I am still dealing with the remaining 10% problems with that knee but they felt much better. I know my observations are by no means a study but I know how my body feels. My old knees feel good on very firm groomers and bumps on the 74's , eastern and western packed powder on the 83's and powder days on on the 95's. I ski about 40 days a year and every year is different but I could feel the difference in the stress I felt on the knee with the wider ski . I know I am closing in on my days with these knees and hopefully the replacements that I properly will have some day will provide me with lots of years left skiing but I will be leaning towards the narrower ski for the conditions every time.

Couldn't resist offering a few illustrative photos to this post showing Brad's old knees holding up nicely
JHMR

Grand Targhee

 

[ScotsSkier]

.....when they are >67mm waist....