Exercise Benefits, Knee, Prehab

ACL Injury Prevention

Watch enough professional sport and you’re bound to see a gruesome ACL injury. Of course, they’ll replay it several times just to drive home the point that the poor athlete is going to spend the next few months of their lives rehabbing. They’ll writhe around in pain as their teammates wave for help, before eventually being stretchered off, or occasionally they’ll try to hobble off giving the clueless commentators hope of it being a minor injury.


The Anterior Cruciate Ligament (ACL) is  one of the four major ligaments that’s responsible for stabilising the knee through all the rigors we subject them to. The ACL gets major attention for athletes as it usually results in a surgical intervention and has a longer road to recovery than most other knee injuries.  ACL injury was often thought to occur as a freak accident and be largely unpreventable. However, looking through recent research paints a very different picture.


A patient’s toolkit while going in for an ACL reconstruction.

Researchers analysed the cause of ACL injury in professional sport (Australian Rules Football) and found that ACL injury can occur in the following ways:


32% full contact

12% due to partial contact

56% as non-contact


ACL injury as a result of direct or indirect contact is fairly tough to prevent, but 56% as a non contact injury is a remarkably high figure. It’s expected that an even greater percentage is expected in amateur athletes due to a slower response time.

Of the non contact injuries:

42% occurred as a result of a sidestep

29% occured while landing

13% occurred during a land & sidestep

Using biomechanical testing, it was identified that increased load on the ACL was observed during knee extension + knee compression + internal rotation + knee valgus

ACL injury

So far, it sounds bleak. Jump, land or cut and brace yourself for a random and excruciating injury. But before we all go and quit our sports altogether let me get to the silver lining: our thought processes and decision making can greatly affect the amount of loading on the knee. Research has found that there is a common chain of events in a non contact ACL injury:

Planning action –> Opponent reacts –> Player changes mind –> Attempt to change body position last minute –> ACL Injury

The reason that researchers have identified is related to the upper body position relative to the knee during athletic movements. During normal events the core muscles have the ability to stabilise the trunk which creates a normal load on the knee. However, add a last minute decision change (as was true of many ACL injury cases), then the core muscles can’t respond quickly enough to brace adequately. Thus resulting in more lateral trunk movement and increasing the forces on the knee, culminating in an ACL injury.

The sidestep was shown to have the greatest load on the knee, with forces being able to snap the ACL every time if not for the muscles. As young athletes watch and mimic their professional counterparts, poor sidestepping techniques become an increasing issue. Especially of concern is the faking in one direction with the upper body before stepping to the opposite side. This movement can put the ACL in the most vulnerable position.

ACL Injury Prevention

Let’s be honest, this is what we are all interested in. How can we use the information that research has shown us in order to help reduce the risk of ACL injuries as well as most other knee injuries.

The priority is to improve dynamic balance and trunk position during athletic movements. Additionally, through coupling balance training with dual tasking in order to better harmonise the brain and core trunk stability.

ACL Prevention

Sport Specific Dynamic Balance

Phase 1: Static Balance

Initially, incorporating static balance into a training regime is vital to ensure that the athlete is building the core and stabilising muscles from the ground up. Static balance exercises should incorporate a static hold for 30 seconds or longer in a stationary position.

  • Single leg balance
  • Prone Plank
  • Glute Bridge
ACL Injury

Plank – Static Balance Training

Phase 2: Dynamic Balance

After the athlete is competent at at static balance, it is then necessary to increase the challenge on their core stability by adding a dynamic component to the tasks. That is, ensuring their trunk is stable during movements of the limbs.

  • Single leg squats
  • Single leg romanian deadlifts
  • Bosu ball training


Phase 3: Dual Task Training

This involves combining static or dynamic balance exercises with a cognitive task relative to the athletes sport. The idea is to train the body to remain balanced and under control even while the brain has to focus on another task. For example:

  • Catching tennis balls on a wobble board
  • Dribbling a basketball while standing on one leg
  • Passing a football while jumping from one leg to another

Phase 4: Sport Specific Training

After training in a controlled environment, the athlete can move to preparing the mind and body in the context of their given sport. As we learned earlier, processing information and having the body react is the prime method of preventing ACL injury, therefore training by way of “reading and reacting” to sport specific stimuli is a vital part of ACL injury prevention training.

For example:

  • Stepping and cutting in response to a defenders movement
  • Reacting to a football’s bounce off the ground
  • Practicing landing and changing direction


An ACL injury can be of great concern for the amateur and professional athlete alike. Although ACL injury might not be entirely preventable, research has given us tools which can reduce the risk of sustaining an ACL injury. By partaking in intensive stability and balance training, the athlete can improve their body’s trunk stability during reactive movements on the sporting field. In turn, the forces acting upon the knee can be reduced which can prevent ACL injury as well as other lower limb injuries.


Product Recommendations

Below are links to some relevant products that can help with ACL injury prevention.

ACL Injury Prevention

ACL Injury PreventionACL injury prevention


Donnelly, C.J., Lloyd, D.G., Elliott, B.C., Reinbolt, J.A. 2012, ‘Optimizing whole-body kinematics to minimize valgus knee loading during sidestepping: Implications for ACL injury risk’Journal of Biomechanics, 45, pp. 1491-1497.
Donnelly, C.J., Elliott, B.C., Doyle, T.L.A., Finch, C.F., Dempsey, A.R., Lloyd, D.G. 2012, ‘Changes in knee joint biomechanics following balance and technique training and a season of Australian football’British Journal of Sports Medicine, 15 March 2012, pp. 7pp.
Donnelly, C.J., Elliott, B.C., Ackland, T.R., Doyle, T.L., Besier, T.F., Finch, C.F., Cochrane, J.L., Dempsey, A.R., Lloyd, D.G. 2012, ‘An Anterior Cruciate Ligament Injury Prevention Framework: Incorporating the Recent Evidence’RESEARCH IN SPORTS MEDICINE, 20, pp. 239-262
FINCH, C., LLOYD, D.G., ELLIOTT, B.C. 2009, The preventing australian football injuries with exercise (PAFIX) study: a group randomised controlled trial’Injury Prevention, 15, pp. 207.


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