Knee injuries

Fact - injuries to the lower leg have always been a problem for alpine skiers. In the earliest years of the sport, fractures of the lower leg bones (the tibia and fibula) were common as the twisting forces generated by a fall were transmitted up unchecked from the ski. The subsequent development of release bindings has been very successful in reducing the incidence of such fractures, but unfortunately has not afforded as much protection to the knee. This joint, with its associated ligaments, menisci and bony structures, currently accounts for approximately 30-40% of all alpine ski injuries.

Although this page focuses specifically on those knee injuries seen from alpine skiing, I am aware that a lot of folk find their way to this page looking for info on knee injuries per se. I hope you do find this page useful and I have added some specific links to other pages on knee injuries which you'll find here. I am always keen to receive feedback on my site so please email me if you have any suggestions about what would make this page more useful to you.

In Scotland , knee injuries occur at an approximate rate of 0.82 injuries per 1000 skier days - i.e, for every 1000 skiers on the mountain on any one day, an average of just under one skier will injury their knee. Looking at it another way, a knee injury occurs once every 1218 days skiing (for an explanation of injury rates and how they are derived, see this page). 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 the latest injury stats show that carving skis are now protective 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. Beginner skiers have only ever skied on carvers and therefore (having experienced no other kind of ski) did not need to adapt. Whilst the majority of knee injuries have a good prognosis, some can lead to significant functional impairment and may even preclude the individual from ever skiing again. Accurate diagnosis, coupled with appropriate investigations and treatment, are essential in aiding the injured skier’s recovery from such injuries as quickly and successfully as possible.

The vast majority of knee injuries seen in alpine skiers involve damage to knee ligaments, particularly the medial collateral ligament. As with other ligament sprains, these are graded from one to three depending on the degree of damage and associated ligament laxity. Laxity is tested by attempting to stretch the ligament open - for obvious reasons, this often can't be done initially as the doctor would end up getting a black eye from the patient. Once pain has settled though (usually at around 5-7 days) the joint can be reassessed.

A minor degree of swelling is usually inevitable with all but the most minor knee injuries, usually developing within twenty four hours of injury. The appearance of significant swelling (i.e. knee looks like a balloon!) within the first two hours of injury strongly suggests the presence of a haemarthrosis (bleeding within the knee joint) which, in approximately 75% of cases, will signify damage to the anterior cruciate ligament. All cases of haemarthrosis should be referred on to an orthopaedic surgeon for further assessment and possible aspiration of the blood from within the joint.

This needs to be done under sterile conditions. Not one to try at home....

An accurate description of the accident coupled with an honest assessment of the individual’s level of ability on skis will suggest the diagnosis in the majority of cases. The direction in which the lower leg moves in the fall will dictate which structure(s) is/are involved and the skier’s velocity will influence the severity of the injury sustained. Beginner skiers are initially taught to adopt the so-called “snowplough” position. This places particular stress on the medial collateral ligament and requires quadriceps strength in order to turn and maintain stability, particularly when a wider - more unstable - stance is adopted (see photo right). With the skis held as wide as this, its difficult to apply full muscular control down each leg and therefore control of one or more ski can easily be lost and the ski usually ends up twisting the lower leg outwards relative to the thigh - doctors have to have daft names for things and this motion is called 'valgus'. The opposite, where the lower leg turns inwards relative to the thigh is called 'varus' but we don't see this as often as valgus injuries from skiing.

With increasing ability, skiers are able to keep both legs parallel which improves the efficiency of turning and allows for higher speeds to be achieved. Whilst this is far more fun than struggling with a snowplough, higher speed can lead to more severe injuries being sustained in the event of an accident simply because the forces applied across the joint are higher.

In the middle is the are the so-called 'stem' turns - part snowplough, part parallel turn - the curse of many a keen intermediate skier desperate to progress to the full parallel turn. If you're at this stage, the danger is trying to ski too fast for your ability to stop and/or down slopes beyond your capabilities. [But we've all done it, author included.....at some stage in our skiing careers]

On skis, one of the most important things you can get into the habit of doing is a daily self test to ensure that your binding settings are appropriate for your individual needs.

Incidence: The commonest alpine ski injury, accounting for 20-25% of all injuries. Most commonly affects beginner and low-intermediate skiers.

Cause: Affected individuals are usually in the “snowplough” position with the knee joint in a valgus position (lower leg leaning out the way relative to the thigh). Injury results from excessive valgus force being applied to the knee joint, either as the result of a fall, the skis crossing, or the snowplough stance widening. In more proficient skiers, usually occurs as a result of unexpectedly “catching an edge” which unexpectedly throws the ski (and thus the lower leg attached to it) outwards.

Presentation/diagnosis: The diagnosis is usually suggested by the description of the fall. Examination reveals tenderness over the medial collateral ligament and pain on weight bearing. The presence of a haemarthrosis suggests a third degree tear, associated damage to the ACL and/or injury to the bony structures of the knee.

Assessment: In the acute phase, pain usually precludes accurate assessment of ligament stability. When possible, this should be performed by applying valgus stress with the knee in 30^o of flexion and the foot in internal rotation (see diagram below left).

Investigation: Often not needed, but radiographs will identify associated bony injuries whilst MRI will detect other soft tissue damage (e.g. to the ACL/meniscus)

Treatment: Grade one and two sprains should be placed in an extension splint until pain and swelling subside. Grade three tears may require surgical repair or the application of a plaster cylinder.

Prevention: Pre- season quads conditioning, correct binding maintenance and release settings and performing the self test can all help to reduce the chances of collateral ligament injury. Avoiding wide snowplough stances which are inherently unstable. Beginners are advised to allow a fall to occur rather than attempting to resist which in turn may lead to more damage.

Incidence: Accounts for 10-15% of all ski injuries (in some studies even higher). Often diagnosed late if at all. Often associated with injuries to other structures within the knee (e.g. MCL and/or meniscus)

Cause: Research has identified three main mechanisms that predispose to ACL damage in alpine skiers. These have been termed the “phantom-foot”, “boot-induced anterior drawer (BIAD)” and the "classic" scenarios.

The Phantom Foot Profile

Approximately 70% of all ACL ruptures from alpine skiing are thought to be caused by the Phantom Foot mechanism. This mechanism occurs when the tail of the downhill ski (which acts as a “phantom foot”), in combination with the stiff back of a ski boot, acts as a lever to apply a unique combination of twisting and bending force across the knee joint. It should be noted that PF ACL ruptures do not require high speeds or steep slopes to occur. Video analysis of more than 14,000 skiing injuries has identified a typical profile comprising of six elements that come together in the event of (usually a backwards) fall and which characterises this mechanism of injury. These elements are:

1) Uphill arm back
2) Skier off balance to the rear
3) Hips below the knees
4) Uphill ski un-weighted
5) Weight on the inside edge of downhill ski tail
6) Upper body facing downhill ski

When all six elements of the phantom foot profile are present, injury to the ACL of the downhill leg is extremely likely. Situations that can predispose to this scenario developing are:-

a) Attempting to get up whilst still moving after a fall
b) Attempting a recovery from an off-balance position
c) Attempting to sit down after losing control

The video clip from YouTube shows a skier who sustains a PF ACL rupture of their left knee after a small jump goes wrong, resulting in them falling backwards. It all happens pretty fast, but watch the uphill ski un-weight, the hips go below the knees, the skier's body faces down the slope and (not very pleasant this) if you turn the sound up you can actually hear their reaction (A loud "Uuh") at the moment the ACL pops.

Boot induced anterior drawer (BIAD)

The boot induced mechanism occurs when a skier lands off balance to the rear whilst attempting a jump. Instinctively, the skiers leg fully extends. As a result the skier lands on the tails of the ski which forces the back of the ski boot against the calf. This pushes the tibia forwards relative to the femur and the ACL tears as a result. A similar mechanism occurs when a stationary skier is hit from behind on the lower leg (usually by another skier or snowboarder). This again applies sudden extreme pressure on the back of the calf, forcing the tibia forwards in a similar manner to that described above with resultant ACL damage.

The video below shows a BIAD ACL injury to a skier who lands to the rear after a jump onto rails. Again, the striking thing is how tame it all is, for such a serious injury to occur. No major speed involved, just a fall in the wrong direction.

Classic mechanism

This mechanism is thought to occur when the skier moves forwards relative to the ski (such as when catching an edge at high speed), a severe anterior bending movement is applied as a result and the forces generated rupture the ACL. There is no video evidence of this mechanism of injury that I am able to post here, and some researchers are sceptical about whether it actually exists or not. Nevertheless, many skiers who have ruptured their ACL (usually in combination with other injuries to the knee, such as to the MCL/meniscus) describe this mechanism after the event. The debate is whether ski bindings play a role in this injury (by not releasing) and whether a reduction in binding settings would lead to a reduction in this injury mechanism. Since the French introduced their AFNOR binding settings, they have seen a reduction in the number of ACL injuries occurring. Its important to remember that this finding is an association, and not definitely "cause and effect" though. There may be other independent reasons why the ACL rate dropped during this time.

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Presentation/diagnosis: Often the individual describes feeling or hearing a ‘pop’ or a ‘snap’, with the knee ‘giving way’ beneath. A haemarthrosis usually develops within one hour of injury. Once the acute swelling has settled, there may be a positive anterior draw sign and pivot shift sign on testing.

Investigation: MRI scanning/plain radiographs to detect associated bony, soft tissue damage and improve diagnostic pick up.

Treatment: Controversial! In the U.K., the general trend is to aspirate the haemarthrosis and initially treat conservatively with splinting and intensive physiotherapy aiming to build up muscle strength to help stabilise the joint. In the US and Europe, early arthroscopy ligament repair and mobility is advocated. Generally agreed that if you wish to continue skiing at the level of a good intermediate or above, you will probably need to have reconstructive surgery to your ACL. If however, your knee feels stable with conservative treatment, this may be avoided. Others advocate a knee brace for additional protection (see below).

Prevention: Education to recognise potentially dangerous situations occurring. In general, always aim to keep arms forward, feet together and hands over skis. The ACL Awareness program devised by Ettlinger et el has been shown to reduce the incidence of ACL injuries by 62% (see reference below). Click here for Carl Ettlinger's website. A new binding development that senses and responds to torque about the femur bone and uniquely provides for lateral release at the heel of the binding, will be ready for the 08/09 winter season. It is certainly the most promising development in recent times offering for the first time potential ACL protection from a ski binding. For more information, click here to visit my page describing this binding or else click here for the manufacturers own website.

Avoiding High Risk ACL Behaviour

1. Don't fully straighten your legs when you fall. Keep your knees flexed.
2. Don't try to get up until you've stopped sliding. When you're down--stay down.
3. Don't land on your hand. Keep your arms up and forward.
4. Don't jump unless you know where and how to land. Land on both skis and keep your knees flexed.

(after Ettlinger et al - see references below)

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TIBIAL PLATEAU FRACTURES

Incidence: Approximately 1% of all ski injuries. Usually affect older, more experienced skiers.

Cause: Severe valgus stress often with compressive forces e.g. as the result of a bad landing after a jump.

Presentation: Haemarthrosis usual. There may be bruising and/or abrasions over the lateral aspect of the joint and an associated valgus deformity of the knee.

Investigation: Usually evident on plain radiographs. CT scanning might be required to determine the exact degree of displacement and area of articular surface involved.

Treatment: If the fracture is displaced or depressed by more than 4mm then surgery is advised to restore anatomical alignment. Frequently these injuries occur at high speed and there is associated severe damage to other soft tissue structures – particularly the ACL and MCL – which will require surgical intervention.

Prevention: Avoiding high jumps and the consequential high compressive forces.

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MENISCAL INJURIES

Incidence: Occur in approximately 5 –10% of all ski injuries, often in association with damage to another structure. Usually affects the lateral meniscus due to a valgus twist in a weight bearing knee.

Cause: Rotational stress applied to a flexed, weight bearing knee. Usually the result of catching an edge at speed.

Presentation/diagnosis: Considerable pain and difficulty weight bearing but may have little swelling. Joint line tenderness is usually evident, especially in the last few degrees of full knee extension. May present with a “locked knee”, where a torn meniscal fragment physically prevents full extension of the joint. Tests for meniscal tears include McMurray’s test (see left) and Apley’s compression test.

Investigation: Imaging may be necessary to exclude associated injuries.

Treatment: A locked knee requires early arthroscopy and repair. Other isolated tears can be managed expectantly with conservative treatment. Severe chondral lesions can be treated with procedures such as micro-fractures, cartilage transplants and biotechnology.

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THE ROLE OF KNEE BRACES

The potential protective role for knee braces, especially in skiers who have had reconstructive ACL surgery, has been a controversial topic for quite a while. In September 2006, Sterett et al from the widely respected Steadman Hawkins Research Foundation in Vail, Colorado published the results of a cohort study in the American Journal of Sports Medicine entitled "Effect of Functional Bracing on Knee Injury in Skiers With Anterior Cruciate Ligament Reconstruction - A Prospective Cohort Study". In this study, 257 skier-employees with anterior cruciate ligament reconstruction wore braces and 563 skier-employees with anterior cruciate ligament reconstruction did not. Sixty-one subsequent knee injuries were identified, 51 (8.9 injuries/100 knees/ski season) in the non braced group and 10 (4.0 injuries/100 knees/ski season) in the braced group (P = .009). Non braced skiers were 2.74 times more likely to suffer subsequent injury than were braced skiers (odds ratio, 2.74 [confidence interval, 1.2–4.9]). Logistic regression modelling identified non bracing as a significant independent multivariate risk factor for subsequent knee injury in the high-demand skiers with anterior cruciate ligament reconstruction. The authors concluded that because of the increased risk of subsequent knee injury in non braced skiers, functional bracing for skiers with anterior cruciate ligament reconstruction should be recommended. They also comment, "Whether the protective effect of functional bracing can be extrapolated to other high-demand patients is yet to be determined." A very interesting study that provides evidence to support what many of us have long felt - that knee braces can protect the knee against subsequent injury.

[Reference - American Journal of Sports Medicine 1 October 2006; Vol. 34, No. 10]

I have now added a separate page to this website focussing specifically on the topic of knee braces for alpine skiing - access it here.

OTHER INTERESTING OPTIONS

CADS

CADS are a device that aim to take the strain off the knee joint when skiing. A weight bypass of the legs is affected by means of a rubber band, a stick, a string, and a harness. The rubber band and the string lift the weight off the legs and on to the stick. That converts the weight your legs had borne into a force down on the ski.
Click on the thumbnail to the right to see an illustration of the device.

According to the manufacturer's website...

"CADS preloads each ski with a pressure derived from stretched, specially engineered rubber bands, which have a much faster response time than human muscles. When approaching a mogul with CADS, the skier’s leg muscles are more relaxed, and thus faster, more flexible and responsive, since some force comes from the stretched rubber bands. When the skis encounter the bump, the legs bend more easily. The upward force on the skis stretches the rubber band, which stores the energy just like the car springs. Upon passing the crest of the bump, the increased force in the rubber bands instantly forces the skis down on the far side of the mogul, maintaining snow contact. Stability and control are dramatically enhanced."

CADS do not make any claims about reducing injury risk and I have no personal experience of this device. However, it does have some research evidence from the renowned Steadman-Hawkins Clinic behind it. For more information, visit the CADS website.

Ski Mojo

Ski Mojos seem to offer a different solution to the same problem - reducing the load on the knees when skiing. They claim that "When skiing, ski~mojo helps support your body weight, taking up to 1/3rd of the strain off your thighs and knees, so your legs have less to do having effectively giving your legs a Turbo-Boost of up to 50%. Like Shock absorbers on a car, ski~mojo is all about control. It improves your stability and smoothes out the ride, giving enhanced performance for less physical effort."

From their website......

"We have used state-of the art materials to produce a piece of precision engineering which meets all of our criteria and the result, ski~mojo has been carefully engineered to give you a constant % level of support that you soon become unaware of as it is comfortable, non - restrictive and works with your body's natural articulation. Essentially the ski~mojo acts as an extra pair of thigh muscles, which support you as you bend your legs and store energy, then support you again as you straighten your legs by releasing energy. Your legs are effectively Turbo-charged. Because unlike your own muscles the ski~mojo stores and releases energy it also acts as shock absorbers. The benefits here are that it reduces the shock to all parts of the body, Smoothes out the ride so that your skis glide better, whatever the snow conditions and as there is a downwards force keeping them in better contact with the snow, your skis edge better, especially in icy conditions when the mojo will react to losing grip far quicker than your brain can. The ski~mojo is attached to your ski-boots by ball and socket type of connections which allows full mobility and it is also strapped to your shins. This ensures that the power units of the ski~mojo stay alongside your thighs and work with them to support you just under your backside without the need for any further attachment. The support given via the Posture strap is always perpendicular to your thighs which means that not only is it supporting you comfortably, it is encouraging you to get your hips forwards over the balls of your feet and this in turn encourages you to flex your ankles and knees, all the things your ski instructor or coach will want you to do. All the component parts of the ski~mojo have been designed and the materials chose so as to be able to take twice the amount of stress and strain that they are required to. This also means that the ski~mojo will survive heavy impacts without breaking thereby spreading the force of any impact over a larger area."

For more information, visit www.skiallday.co.uk

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KNEE INJURY REFERENCES..

Paletta GA and Warren RF. Knee Injuries and Alpine Skiing: Treatment and Rehabilitation. Sports Med 1994 17(6) 411-423.

Ettlinger CF, Johnson RJ and Shealy JE. A Method to Help Reduce the Risk of Serious Knee Sprains Incurred in Alpine Skiing. Am J Sports Med 1995 23(5) 531-537

Langran M, Jachacy GB and MacNeill A. Ski Injuries in Scotland: A Review of Statistics from Cairngorm Ski Area, Winter 1993/4 Scot Med J 41(6) 169-172

Johnson RJ and Ettlinger CF. Alpine Ski Injuries: Changes Through the Years. Clin Sports Med 1982 1(2) 181-197

Mona D ACL Reconstruction and Rehabilitation: A Protocol of Accelerated Rehabilitation. Department of Sports Trauma, Lugano, Switzerland. Presented at 13th International Congress on Ski Trauma and Skiing Safety, Cervinia, Italy. May 1999.

Johnson RJ, Ettlinger CF, Shealy JE and Meader C. Impact of Super Sidecut Skis on the Epidemiology of Skiing Injuries. Sportsverl. Sportschad 1997 11 150-152

Langran M, Selvaraj S. Snow Sports Injuries in Scotland. A case-control study. Br. J Sports Med. 35:135-140, 2002

Miller SL, Gladstone JN. Graft selection in anterior cruciate ligament reconstruction. Orthop Clin North Am 2002 Oct;33(4):675-83

Rossi MJ, Lubowitz JH, Guttmann D. The skier's knee. Arthroscopy 2003 Jan;19(1):75-84

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Useful web links for knee injuries

Assessment of acute knee injuries on the sports field - http://www.physsportsmed.com/issues/1999/10_01_99/laprade.htm

Links to various websites on knee injuries - http://sportsmedicine.about.com/cs/knee_injuries/

Comprehensive list of relevant sites from Medline - http://www.nlm.nih.gov/medlineplus/kneeinjuriesanddisorders.html

Useful information on knee injuries and surgical treatment - http://www.drwaltlowe.com/kneeinjuries.htm

Information on knee surgery - http://www.arthroscopy.com/sp05000.htm

How to avoid a knee replacement - http://www.stoneclinic.com/avoiding_knee_replacement.htm

Knee guru - Great site! http://www.kneeguru.co.uk

Another useful site - http://www.genufix.com/knee_injuries.htm

Bauerfeind AG's website with information on various knee braces and supports - www.bauerfeind.com

Pictorial guide to ACL reconstruction - http://www.arthroscopy.com/sp05018.htm

Guide to meniscal injuries of the knee - http://www.athleticadvisor.com/Injuries/LE/Knee/meniscal_injuries.htm

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