ACL injuries in skiers

How to reduce the risk of ACL injuries in skiers. Part 1

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Years ago, I wrote an article for a British ski magazine on how to reduce the risk of ACL injuries in skiers.  I had some great feedback, bar one lovely gentleman! He emailed me to ask “are you implying that had I done all your exercises I wouldn’t have ruptured my ACL when I skied into a tree”!  To my credit, I answered him very politely.

Can you prevent ACL injuries?

Just in case you were wondering, it is not possible to completely prevent ACL injuries from occurring.  In fact, injury prevention is not completely possible in any sport and anyone who claims otherwise is talking codswallop!  However, there is plenty of research to support the fact that by implementing certain training regimes the risk of sport specific injuries and injury patterns can be reduced.  I know that I have inaccurately used the word ‘prevention’ when discussing ways of reducing the risk of injuries occurring in the past.  However, as my practice has evolved and my understanding of research has improved I try to select my choice of language more carefully.

Because reducing the risk of ACL injuries is such a large topic, I have decided to publish the blog in two parts.  Part 1 aims to look at what the anterior cruciate ligament (ACL) is and how it functions.  We will identify risk factors and injury mechanisms in skiers. Following this we will explore ways of how you can decrease the risk of an ACL injury when you are skiing.

Part 2 will talk more about the physical factors associated with ACL injury.  It will explore ways that you can train to decrease the risk of injury.  There will be lots of examples of ski specific exercises that you can perform at home.

This blog is applicable to skiers of all levels and abilities. Information regarding ACL injuries is also extremely important for ski instructors.  This is from both a personal point of view and professionally in terms of teaching.

The impact of ACL injuries

ACL disruption is problematic to skiers of all levels, both physically and psychologically. An ACL rupture has a substantial impact on ability to work and earnings, quality of life and day-to-day function. Unfortunately, if you rupture your ACL you may need surgery.  This is usually followed by up to nine months of rehabilitation.

One study carried out over 25 years looked at the incidence of ACL injuries in elite French national team skiers between 1980 and 2005. The data collected showed that more than 28 % of female skiers and 27% of the male skiers sustained at least one ACL injury from a skiing accident. This means that more than a quarter of these competitive skiers suffered an ACL injury! This highlights the need to reinforce the importance of ACL injury reduction strategies.

ACL disruption makes up a large portion of ski injuries. It is every skiers worst nightmare. They fall, they hear a pop, there is a moment of agonising pain and when they try to stand up their knee gives way.  The following signs and symptoms may occur with an ACL rupture:

  • You may hear or feel a pop or snap
  • There is acute pain but this may only last for a short duration
  • The knee swells within a few hours
  • The knee feels very unstable and may give way.

What is the ACL?

ACL stands for the Anterior Cruciate Ligament.

Ligaments connect bone to bone. The ACL is one of the four main stabilising ligaments of the knee. It starts from the front of the tibia (the shin bone) and twists up and backwards to join the femur (the thigh bone).

The anterior cruciate ligament


What does the ACL do?

The ACL prevents the shin bone (tibia) moving excessively forward on the thigh bone (femur). This helps to stabilise the knee and allows the joint to bear loads correctly.

How is the ACL injured in skiers?

The ACL is made of tough, fibrous tissue. However trauma to the knee can cause it to tear or rupture.

Twisting, pivoting and strenuous landing movements can all affect the ACL. The following are well recognised mechanisms of ACL injury in skiers.

1- Forward Twisting Fall

A forward twisting fall may account for more than half of all ACL injuries in recreational skiers.

A valgus-external rotation force occurs when catching an edge of the ski when executing turns. This means that the knee bends inwards and twists outwards.

2 – The Phantom Foot Mechanism

This is basically a backwards twisting fall.  It can occur to the leg of the downhill ski during a sudden loss of balance or control. Phantom Foot injuries occur when a skier is off-balance to the rear with their hips below their knees. The downhill knee is subjected to internal rotation (twisting) and bending forces. As a result there is a combination of a strong quadriceps contraction applying an excessive force to the shin bone along with the lower leg stuck in a rigid ski boot in a binding that fails to release.  The strain from this type of fall has to be taken up somewhere and it is usually the ACL which suffers.

This can occur if trying to get up while still moving after a fall, recovering from an off-balance landing, or attempting to sit down after losing control.

3 – The Boot Induced Mechanism

This tends to occur on heavy impact and hard landings when the skier becomes off-balance to the rear. The ski continues to move forward while the pressure of the boot against the back of the leg increases. At the same time, the muscles of the skier’s leg automatically contract to hold the leg in a fully extended position. The leg is unable to absorb the jarring impact and the back of the boot drives the tibia out from under the femur, thereby tearing the ACL.

4 – Collision Mechanism

This occurs when a skier is hit from behind on the lower leg. The impact forces the shin bone forward which causes damage to the ACL.

5 – Catching an edge at high-speed

The inside edge of the front of the ski becomes impacted under snow. The involved limb begins to draw away from the body and rotate outwards while the skiers momentum carries him/her forward. This usually occurs skiing at high velocity in poor conditions.

What should you do if you suspect that you have an ACL tear?

Firstly, seek medical advice. A doctor will usually perform an x-ray on your knee to ensure that there is no bony damage associated with the injury. However, an x-ray will not show an ACL rupture. For this you need an MRI scan, but even a scan cannot always be 100 % reliable.

A doctor or physiotherapist can carry out a series of manual tests to see if they think an ACL injury has occurred. Managing the swelling is extremely important. You can use the POLICE acronym.

Protection. To prevent further damage and to allow the knee to rest to encourage healing you will need to protect the joint.  This is especially true if it is giving way. A knee brace and crutches may be given to you when your injury initially occurs.

Optimal Load. This means starting early rehabilitation so that you can maintain as much strength through the knee as possible.

Ice. Wrap some ice in a cloth. Place it over your swollen knee for 10 – 15 minutes at a time. You can repeat this every couple of hours.

Compression. Tubigrip or an adhesive bandage works well.

Elevation. The higher the better!

ACL injuries in skiers

Manual testing of the ACL

Having a good understanding of your injury will greatly help you manage on the road to recovery. The sooner that you see a physiotherapist and begin rehabilitation, the better the long-term prognosis. It is essential to learn how to maintain muscle strength and regain range of movement as soon as possible.

What next?

ACL surgery is a whole new topic in itself. Not everyone will need an operation. However, in the majority of cases if you are keen to return to skiing, surgery may be advised. However, there are many cases where surgery has been avoided by intensive rehabilitation. Whether or not you should have surgery or manage your knee conservatively is best discussed with you doctor, physiotherapist and surgeon.

There is no evidence to support the need for immediate surgery after an ACL rupture. It is usually preferable to let the swelling settle before operating and this can often take 6 to 8 weeks.

Risk factors for an ACL injury in skiers:

  • Environment – poor visibility and difficult conditions and poor safety awareness.
  • Gender. In some sports, due to anatomical and hormonal factors females are at higher risk than men. However, in skiers this is under debate.  It has been suggested that in recreational skiers, women are more at risk.  However, in competitive skiers, the number of ACL injuries is similar in men and women.
  • Foot position. If you have a tendency to over pronate (feet roll inwards) your knee-joint may be under a lot more strain.  This may put your ACL in a vulnerable position. Good boot fit and accurate orthotics are essential.
  • Inaccurate equipment set up, especially din settings. If your bindings don’t release in a fall then the chances of the ACL rupturing are a lot higher.  It is extremely important not to exaggerate or under-estimate your level of skiing (or your weight) when you are having your equipment fitted.
  • Poor strength and fitness levels.
  • Decreased agility and flexibility.
  • Poor proprioception, balance and coordination.
  • Poor biomechanics and alignment leading to structural vulnerability
  • Muscle imbalances leading to inefficiency and fatigue

ACL Injury Reduction Strategies

There is more and more evidence emerging stating that ACL injury reduction programmes are effective and should be implemented into high risk sports.  However, it is evident that little of this research has been carried out with skiers.  Nonetheless, many of the strategies that have been put into practice in other sports can be applied to skiers in a sports specific manner.

A study in the United States implemented a training programme which focused on awareness and education in skiers.  Strategies included avoiding high-risk behaviour and positioning, recognising potentially dangerous skiing situations and responding quickly to unfavourable conditions. They found that using this program reduced the rate of serious knee injuries in skiers by 62% (Ettlinger et al. 1995).

How to help reduce the risk of an ACL injury?

In this blog we will start to introduce ways of reducing the risk of ACL injuries.  In part 2 we will delve further into strategies that recent research has shown reduces the risk of ACL injury in high risk sports. It is a multifaceted approach that incorporates a number of approaches that work in combination to minimise the risk of injury occurring.

Education and Awareness

As mentioned earlier, education and awareness of ACL injuries and how they occur can largely decrease the chances of them happening. It is important for skiers, especially instructors to recognise and convey the risk of potentially dangerous situations.

Even having an understanding of how to fall in the safest manner can dramatically decrease the chances of rupturing your ACL. When falling, to reduce twisting forces through the knee try to bring your arms forward with your hands over the skis and keep your feet together.  If you can remember to do this, I am impressed!  Despite supporting these recommendations, I know that I would struggle to remember these principles if I was tumbling!

It is also important to avoid attempting to get up while still moving after a fall and to avoid attempting to sit down after losing control. If you do fall, keep your knees bent. Don’t try to stand up until you have completely stopped sliding.

Follow us on instagram or facebook to be made aware of when we publish part 2. Here we will look further at biomechanical factors and how to train to reduce the risk of ACL injury.

* References: Ettlinger CF, Johnson RJ, Shealy JE. A method to help reduce the risk of serious knee sprains incurred in Alpine skiing. Am J Sports Med. 1995;23:531-537
* Pujol N, Rousseaux Blanchi MP, Chambat P. The Incidence of Anterior Cruciate Ligament Injuries Among Competitive Alpine Skiers. A 25 year Investigation. Am J Sports Med 2007;35(7): 1070 – 1074
* Ruedl G, Webhofer M, Linortner I, et al. ACL injury mechanisms and related factors in male and female carving skiers: a retrospective study. Int J Sports Med. 2011;32(10):801-6.
* Shimokochi Y, Ambegaonkar JP, Meyer EG, Lee SY, Shultz SJ. Changing sagittal plane body position during single leg landings influences the risk of non-contact anterior cruciate ligament injury. Knee Surg Sports Traumatol Arthrosc. 2013 Apr;21(4):888-97.

Disclaimer: The purpose of this blog is to provide general information and educational material relating to exercise, physiotherapy and injury management. ALP has made every effort to provide you with correct, up-to-date information. In using this blog, you agree that information is provided ‘as is, as available’, without warranty and that you use the information at your own risk. We recommend that you seek advice from a fitness or healthcare professional if you require further advice relating to exercise or medical issues.

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