Why Are There So Many ACL Knee Injuries Skiing?

 "Just as I fell I heard a' pop". Any skier who has ruptured their ACL will know that for such a small sound, 'the pop' is a massive harbinger of a world of pain, not only the instant agony and trauma to the knee but also the long term torment of repair and rehabilitation before contemplating skiing again.

Although the number of general injuries while skiing such as a fractured tibia has fallen significantly over the past 30 years thanks to better designed bindings, damage to knees has increased accounting for a third of recreational alpine skier injuries according to a six year survey. And the most common knee injury of all is a rupture of the anterior cruciate ligament (ACL).

THE LACHMAN TEST

Of course, not all knee ligament injuries are ruptures. Some are tears rather than actual severing of the ligament - and there are varying grades of tear with different prognoses in order to ski in the future from the need to wear a knee brace for support to full reconstruction surgery.

And you'll know the difference between a tear and a rupture as soon as you try to stand let alone ski after falling. With a full rupture of the ACL let alone a triple whammy of the 'terrible triad', the ACL, MCL and meniscus, your leg will immediately buckle unable to take any weight so the bloodwagon or heli is the only way down the mountain.

The defining Lachman test is carried out by a doctor or physio who will tug the knee forward and sideways testing for a functional knee ligament. If the only resistance is your plea for mercy then chances are your ligament is ruptured. However, even MRIs can be deceptive, so surgery is often the only way to know for sure.

According to top UK consultant orthopaedic surgeon, James Lewis, repairing a torn ACL is increasingly successful: "We have a greater understanding of which sub-types this works best for - ideally when the anterior cruciate ligament has torn of the femur (thigh bone) rather than in the middle of the ligament," he says in a Style Altitude interview, Knee Injuries From ACL to Knee Replacements.

SKYROCKETING SURGERY

If you ski, chances are you know more than one person who has heard that 'pop' and gone under the knife for reconstruction, spending at least six months rebuilding their quads, which have shrivelled to the size of chicken legs from lack of use.

Most recent figures reveal that more than 100,000 ACL reconstruction surgeries are performed in the US each year. The injury is skyrocketing among 14-18 year olds, and has increased by 147.8 percent over the last 10 years, and 2.3 percent annually, according to the American Academy of Pediatrics.

Women seem slightly more prone to ACL tears, with explanations due to women's physiology ranging from more risk pre-menstrual cycle to wider hips and their proportional less leg muscle mass to men.

REASONS FOR ACL INJURIES

A Google search questioning just why there are more ACL injuries, these days, throws up a few articles discussing the reasons, with lack of appropriate warm-up stretching and strengthening exercises being blamed especially for sports such as football where ACL damage is common due to that foot plant and quick leg twist movement.

It's that rapid change of direction, which also comes with skiing, that can cause ACL injury. In fact, ACL and meniscus injuries are highest in skiing and soccer, according to epidemiological data. But with the wide range of ages and abilities of skiers who rupture their ACLs there is obviously more than one reason why mountain hospital A&E departments are seeing more patients being bloodwagon-ed in with this knee injury.

So what are the reasons for the increase in skiers rupturing their ACLs?

THE PHANTOM STRIKES

Number one most identified culprit is the 'Phantom Foot'. With the tail of the skis acting like a lever pointing in a direction opposite to that of the human foot, the combination with the stiff back of your ski boots, can result in unnatural twisting and bending of the knee. According to Vermont Ski Safety there are six elements contributing to Phantom Foot knee damage:

• Uphill arm back
• Skier off-balance to the rear
• Hips below the knees
• Uphill ski unweighted
• Weight on the inside edge of downhill ski tail
• Upper body generally facing downhill ski

Although these elements may fall into place in almost any order during a sudden loss of balance or control, the list shown here is characteristic of the chain of events which can often put the average skier at risk.

But ask anyone who has suffered this debilitating injury and many will admit "I wasn't in control of my (speed) (landing) (turn)" and it's that moment when mind disconnects from body when disaster often happens.

FLIPPING UNFORTUNATE

The increase in freestyle skiing including the 'fridge kid' generation who flip from ramps and skid off boxes in snowdomes have, for sure, upped the number of ski related injuries especially among younger skiers, with knees just a part of collateral damage.

Loulou was 22 years old, working for Crystal in Tignes, when on Christmas Eve she snapped her ACL while out riding with friends in the park. "Once breakfast had been served and rooms cleaned, all thoughts turned to clipping on those skis and getting on that hill," she recalls, "With new rollers in the park the challenge was to try and get as much air as possible. After landing the darn jump, I stupidly decided to turn around to see if my friend had landed it after me.

"It may sound overdramatic but I have genuinely never regretted anything more in my life than looking back over my shoulder and twisting round in my skis to then feel my knee ‘pop’, my skis cross and a pretty big wipe-out to follow.

"Although in the back of my mind I knew that I had done something pretty bad, I clung onto the idea that it was Christmas Eve, my season had just started; these serious injuries happen to punters on a week’s holiday, not second-timers with new park skis and a recently upgraded lift pass."

But it's not just skiers who suffer knee ligament ruptures. Snowboarder, Billy Morgan, Big Air Olympic bronze medal winner in PyeongChang, 2018, snapped both his ACL and MCL knee ligaments six months before the Sochi Olympics four years earlier, In an interview with The Times he admits, “I was at a snowdome doing a front flip, just messing about. My knee folded inwards, cruciate ligament snapped".

CARVING CULPRITS

But while a triple cork is just one wrong twist away from knee injury, for the majority a ruptured ACL follows a less dramatic fall.

ACL ruptures make up 50 percent of all knee injuries specifically among recreational athletes, according to Jag Bains, MSc Physio, Bachelors in Kinesiology & Psychology, who works out of Physiostation & Sports Injury Clinic in Surrey British Columbia Canada. He has a specialist interest in knee rehab, specifically ACLs. He believes that carving skis are a major culprit for skiing ACL injuries.

"Carving skis seem to catch an edge more than traditional skis," he explains, "This results in a forward twisting fall putting greater strain on the ACL."

According to The Orthopaedic Journal of Sports Medicine, equipment-related knee injury factors from carving skis are due to: 'shorter length, changed flexural and torsional stiffness, enhanced side cut and the increasing distance between the ski boot and snow due to lifters, contributing to changed knee injury patterns within recreational alpine skiers during the last decades. The introduction of the carving skis has led to different complex injury situations and the forward twisting fall still represents the most frequent type of fall among ACL-injured skiers'.

ARE ALPINE BINDINGS TO BLAME?

But if your carving ski has delayed release or doesn't comes off, as you twist and fall injuring your ACL, then should we blame the bindings and not the ski?

Even though downhill bindings have minimised ski injuries drastically over the past 30 years thanks to their ability to release the foot under pressure of a fall and the universal use of DIN settings, there's an argument that while protecting ankles and lower legs from twists and fractures, they actually deflect the trauma upwards to the knees.

The DIN - Deutsches Institut für Normung - internationally recognised standard, revolutionised ski bindings, providing a common tension scale for the tightness of bindings with settings ranging from from zero to 18. So downhill alpine bindings can be set to release according to a host of data including weight, height, age, ability, ski boot length and terrain.

Of course, not everyone follows the DIN rules. Some will cautiously use a lower DIN setting so their bindings release quicker thus risking unnecessary but usually less catastrophic falls. A few extreme freeriders will crank up their settings so high that their skis won't come off at all, ironically for their own safety - for instance, when in no-fall terrain.

SKI BINDINGS FOR KNEES

Significantly there have been few changes to the design of alpine ski bindings although touring bindings have been revolutionised over the past few years thanks to necessity being the mother of the invention of lateral toe release mechanisms for pin bindings

Until recently there was only one alpine ski binding on the market specifically designed to protect the knees. In 2009, KneeBinding of Stowe patented their third release mechanism specifically designed to react to the forces known to cause most knee injuries in skiing and to release before those forces can damage the knee.

This was the only binding to offer protection against soft tissue knee injuries. Two independent studies involving 1600 participants at 13 ski resorts over three season compared ski-related knee injury rates for resort employees skiing on these bindings to traditional release alpine bindings. KneeBindings reduced the risk of all ski-related knee injuries by 75 percent compared to all others.

But now we have a new knee preserving binding on the market, the PROCTECTOR, created by Tyrolia currently available on Head and Elan skis.  The innovative full heel release function of this binding is meant to reduce ACL strain by more than 50 percent.

DEEP IMPACT

The increase in freeriding and the fact that more people are skiing deep powder because of the introduction of wider skis have made it easier, has without doubt, also, impacted on the number of knee injuries.

This is mainly because 'powder' is not always the true definition for the snow state in the backcountry or off piste. Powder can be condensed to feel like skiing in setting concrete. It can also change in a blink of an eye or start of a turn, according to the sun and wind effect plus the slope aspect and incline, so you can be skiing heavenly powder one minute and heavy sludge the next, a recipe for disaster for expert backcountry skiers let alone off piste intermediates.

Steve, 61, was off piste when he hit gnarly crust, "I lost control and came to a sudden stop, my bindings released," he remembers, "I managed to walk to the piste but when I tried to put my skis back on my right knee was all over the place, and the bloodwagon was called." (See main image). 

The more people skiing powder, the more potential there is for injuries, especially knees if bindings don't release or windblown crud clamps your lower legs while your upper body is in full motion turning in another direction.

SLIPPERY SLOPES

So stick to the pistes? Except, of course, there are many accidents on the pistes that also cause knee damage, especially when it comes to manmade snow.

With a higher moisture content, artificial snow is made of micro-balls of ice that are far from powdery. It ices up quickly, often creates a polystyrene type hard crust overnight and can be four times harder than snow, bringing not only a high risk of sliding and falling but, also, of injury. Ask any skier who competed at the last Winter Olympics in Bejing, the first games to use 100 percent artificial snow and they'll tell you just how slippery it was - and painful to fall on.

But, closer to home, we asked Dom Hickey, 34, who has skied all his life in Serre Chevalier without injury. At the end of last season, in March, when many of the runs were topped up by snow cannons due to the lack of snowfall, he slid off the piste when travelling at speed but well within his normal control limit.

"I just looked over my shoulder to check on my friends following, when my skis skidded on the hard, icy piste". It was this twist and skid that resulted in his ACL tear. His DIN setting was on 8, in line with his skiing expertise and the fact he'd been skiing "hard and fast all morning" so, yes, the bindings did work and his skis came off with the fall. 

ENDING IN TEARS

So a fall can happen to the most expert skier but it is also how you fall that can be the difference between getting back up to ski or waiting for a heli ride to the hospital.

It is possible to minimise damage by going with a fall. But who wants to fall? Many have a fear of falling, which makes it more likely to end in tears (tears as in crying and tears as in ligament). Fighting to stay upright can create injury because inevitably you do fall but with tense muscles and awkward twists. Only if it's a steep icy couloir is it wise to try NOT to fall. Lose the fear but don't lose all sense of survival.

However, when we asked how did they rupture their ACLs, every skier we asked, reported that it all happened so fast they had no time to think about saving themselves - let alone their knees.

RIPPED TORSO OR RIPPED LIGAMENT

Can we blame knee injuries on lack of fitness?

This would hold true if the majority of ACL ruptures was among unfit skiers on their one week's holiday. But even ski-fit seasonaires are not immune. According to a recent report posted by KneeBinding on average soft tissue knee injuries account for nearly half of a ski resort's total compensation claims from employees who are working there for the whole season. See Loulou's ACL rupture story, above.

There are plenty of exercises aimed at ski fitness using weights and/or cardio. And, as with any sports, a warm-up can help prevent injury. Jag Bains, physio, recommends a pre-ski warm up consisting of: "Single leg exercises (single leg Romanian deadlift  with rotation, single leg squats), plyometrics (force absorption squats bilateral/single leg, mini jumps with rotation landing with depth), and ensure to include core and glute activation. 

"Additionally a study by Westin et al, looked at an outdoor warm-up by the Swedish Ski Federation, with an indoor core and neuromuscular control based exercises (hopping and landing). This study found a 45 percent injury risk reduction during the prevention period."

EVERYBODY LOOK TO THE LEFT

According to the Swedish Ski Federation research, there is more risk of suffering a serious knee injury to the left leg compared to the right when alpine skiing because of a natural imbalance. To help prevent this, they have devised a series of exercises ranging from single leg hops on one leg to skiing with the inner ski lifted, aimed at equalising leg strength and minimising the potential for ligament injuries.

RUPTURE, REPAIR, REPEAT

Among the 100,000 ACL reconstructions performed in the US each year some, of course, are repeat repairs. Research shows that a very high percentage of athletes with an ACL tear will go on to rupture the same knee or injure the ACL in the other knee. Re-tear rates are around 20-25 percent meaning one in every four to five athletes are suffering a second ACL tear.

Doing your ACL once is a pain (literally and metaphorically), rupturing your knee ligaments twice - or both legs - is excruciatingly bad luck and explains the massive increase in knee brace sales.

I-Ling, 51, a beginner skier first ruptured her ACL during ski lesson No 4 on a blue run in 2019, had reconstruction 11 months later and then re-ruptured it during ski lesson No 14 in March 2022. 

The second fall was at the end of the lesson and on a different pair of skis. "I was tired," she remembers, "Plus I didn't seem to be able to control the skis. In short, not my day. Final home stretch then the lesson would be over and I could go home. I got ready to glide down but at the very last second I somehow changed my mind and turned in the opposite direction trying to stop. As I fell the 'repaired knee' was injured again." 

THE LAST LEG

"I was tired." We've heard this many times from ACL tear victims when tired legs at the end of a lesson or day's sking  has set a skier up for a fall and knee injury.

Doug, 32, suffered the double whammy of ACL and MCL ruptures, this year, while working in Whistler after what he admits was "a massive morning of big skiing - hikes, hucks and all'. With half an hour to kill before a late lunch, he went for one last lap. "We decided to take the blue down instead of hiking up to the bowl, again," he says, "So we had a fast and loose blast down, going off the side of the piste to hit a couple of wind lips. For the first one, my legs were all over the place, for second one the same but when I landed my left ski caught the outside tip and rotated in suddenly, digging into the snow and stopped, causing my whole body to land down on top of it as it twisted."

An experienced freeride skier, Doug had his DIN setting at 10.5. "Not crazy, but a little higher than I'd normally have them," he admits, "But we'd been pushing hard earlier in the day."

So, no, his bindings didn't release.

And, yes, it was his left leg. 

AGEING KNEES

They're not over the hill, they're on the hill. More pensioners are skiing into their twilight, no midnight years. According to the National Ski Areas Association, 5.3 percent of downhill skiers on the slopes are over 60 and that number is rising.

Knees are one of the first joints to show signs of ageing, accounting for the increase in partial and full knee replacements - and for age to be the reason for giving up impact sports such as skiing. But there are many procedures to repair and renew knees, as discussed by top orthopaedic surgeon, James Lewis, in Ski Injury from ACL Repair to Knee Replacements that can result in many more years of skiing.

But being over 60 can affect the outcome of an ACL injury. Reconstruction operations for POWS (Pensioners On Wide Skis) come low down on the long waiting lists for hip and knee replacements.

When Steve, 61, tore his ACL off piste, as described above, the NHS in the UK would not operate. "The recovery was deemed to be worse and not completely guaranteed to be totally successful because of my age," he comments. "Intense physiotherapy was recommended instead. But I was running and cycling within a couple of months and skied January the following season with the aid of a DonJoy brace, that I still use today for skiing. Even though my knee is now fully stable, I dare not kick a ball."

KNEE BRACES FOR SKIING

At least, there is plenty of choice for knee protection, which can lessen the potential for re-injury. These can vary from the traditional hinged knee braces including the DonJoy, popular for skiing, to the very innovative Stoko, the latest alternative for knee protection.

Stoko supportive tights with built-in cable systems have been created by 27-year-old CEO and Co-Founder Zack Eberwein, a mechanical engineer who came up with the concept after suffering multiple acute knee injuries and worked with physicians, physiotherapists, engineers, Olympians and a diverse range of passionate athletes to design the unique Stoko solution to knee injury.

The Stoko K1 has been tested by our Tech Editor, Gavin, 62, who's not only an expert in all things tech for skiing but also an authority on knee injuries and braces.

He first ruptured his ACL skiing from powder to crud in the backcountry in France, 10 years ago, resulting in a heli-ride to Briancon hospital, and months of pre and post-operation rehab protocols.

Then in 2020 he fractured his kneecap catching a ski on a hidden tree branch and head planting in the Japanese pow but carried on skiing for the rest of the week helped by packing a lightweight brace, just in case of a knee tweak - an incasey bracey!

He's walking, cycling, running AND skiing proof that there is active life after a knee injury, although he now draws the line at skiing potential knee rupturing boiler-plate pistes.

Style Altitude has no affiliate arrangement with any brand or retailer and will not profit from any sales made through links in this feature.

References:

Posch, M., Schranz, A., Lener, M., Tecklenburg, K., Burtscher, M., & Ruedl, G. (2021). In recreational alpine skiing, the ACL is predominantly injured in all knee injuries needing hospitalisation. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA, 29(6), 1790–1796. https://doi.org/10.1007/s00167-020-06221-z

Westin, M., Harringe, M., Engström, B., Alricsson, M., & Werner, S. (2020). Prevention of Anterior Cruciate Ligament Injuries in Competitive Adolescent Alpine Skiers. Frontiers In Sports And Active Living, 2. doi: 10.3389/fspor.2020.00011