The Knee - ACL Injuries Part Three

Can You Actually Prevent an ACL Injury?

Well-designed prevention programs can cut ACL injury risk by up to 30% — and take just 20 minutes, a few times a week.

Here's the science behind the modifiable risk factors, and the programs proven to work.

ACL injury rates are on the rise, particularly in younger populations and in females. In Australia, part of this is down to the rapid growth of dynamic sports like AFL, rugby and soccer among women — but as we covered in Part One, plenty of other factors are at play too.

In this final part of the series, we look at the risk factors you can actually change, the programs designed to reduce risk, and what the evidence says about whether they work. Spoiler: it's pretty good.

What you can't change — and what you can

As discussed in Part One, some ACL risk factors simply aren't modifiable — gender and anatomy among them. Prevention programs are interested in what is modifiable, and that comes down to the neuromuscular system: the network that controls movement in your muscles and skeleton. The good news is that this system is adaptive. We can change it.

The four modifiable risk factors

• Movement and alignment — how does the knee move? Are there restrictions above or below it (a stiff ankle, for example, increases load on the knee)? How well do the glutes control the knee's position during dynamic movement?
• Strength — good quadriceps, hamstring, glute and trunk strength is essential for knee control. Weak quads reduce knee flexion; weak hamstrings, hip abductors and core muscles can all push the knee into a more vulnerable, valgus (knock-kneed) position.
• Ground reaction forces — the force the ground applies back through the body. Weaker muscles mean more of that load transfers to joints and ligaments instead of being absorbed.
• Fatigue — as we tire, motor control drops off, which worsens all of the above: strength, movement patterns, reaction speed, and how much load ends up going through the joints and ligaments.
• 
  

It might sound like a lot, but a well-designed exercise program, paired with targeted physiotherapy input, can bring all four of these factors under control.

Do prevention programs actually work?

Yes. Over the past decade there's been an explosion in programs designed to reduce ACL injury risk, many built by sporting bodies for their own athletes — think the FIFA 11+ program for soccer, Netball Australia's KNEE program, and the AFLW's Prep-to-Play program.

The FIFA 11+ program is reported to reduce ACL injury incidence by around 30%.

Several systematic reviews have found similar reductions with the PEP program, and clinical practice guidelines published in 2018 (Arundale, Bizzini, Giordano et al.) concluded that exercise-based knee injury prevention programs have strong, well-supported benefits for reducing both general knee injuries and ACL injuries specifically, with very little risk and minimal cost.

Better still, these programs can be delivered safely and effectively by coaches, parents, health professionals and sports trainers — not just physios. That said, they're not a cure-all. Good clinical assessment, treatment and targeted intervention are still essential parts of the overall picture.

What's actually in these programs?

Despite their different names, all these programs share the same building blocks: flexibility, strength, plyometrics, balance and agility, and running mechanics. Done regularly, this combination reduces the risk of knee injuries broadly, including ACL injuries specifically.

Making it a habit

If you've injured your ACL before, an ongoing prevention program should become part of your weekly routine — as automatic as washing your hair or putting the bins out. It doesn't need to be arduous: most of the programs above are designed to take about 20 minutes, 3 to 4 times a week, and can be adjusted to match your changing capacity. Our classes and GLA:D program are a great place to build this into a sustainable routine, with expert guidance along the way.

The take-home

Stay in touch with your physiotherapist — they're the key professional for your knee health now and into the future. A simple check-up to monitor strength, range of motion and functional control against your baseline can help you stay active for longer, with happier, healthier knees.