PHYSIOTHERAPIST + DIRECTOR
The science behind why ACL injuries occur, and, more importantly, how to limit the possibility of sustaining an ACL rupture yourself.
The anterior cruciate ligament, commonly referred to as the ACL, is one of the four primary ligaments that act to stabilise the knee joint. This particular ligament prevents excessive movement between the thigh bone (femur) and the larger shin bone (tibia), allowing you to develop huge amounts of force through the knee without any feeling of instability. Although very strong, the ACL is designed to protect primarily against forward movement of the shin bone and the tight bone, but is not particularly effective at preventing twisting of the shin bone relative to the thigh.
As a result, the ACL is most commonly damaged in a position where the bent knee falls into a position that cases rotation between these bones, such as the knee falling sharply inward as you change speed or direction of running. The interesting statistic is that up to 80% of ACL injuries are reported as ‘non-contact’, meaning that most people injure their knee without any kind of traumatic force being applied.
The classic injury is reported as:
• Weightbearing injury, knee twisting, instantly gives way
• Sharp change of speed or direction
• Hearing ‘pop’ or ‘snap’
• Instant deep pain with early, large swelling
• Unable to continue play, often early feel of instability in weight bearing
Here in Townsville we see a very high incidence of ACL injuries, possibly due to the hard ground or thick grass types that grow here. We would love to see less people come through the door with such injuries, so here are some evidence-based strategies to reduce your risk. Such preventative interventions have been shown to decrease risk by up to 89% in large athletic populations.
1. Strengthen your glutes
Multiple studies have shown that a weakened glute limits your ability to control you knee position under stress. When the knee in not in the optimal position during loading there is a reduction in the ability of your quads and hamstring to complete their function, which is in part, to stabilise the knee. Strengthening the glutes through hip extension or abduction based exercises will improve your ability to actively position your knee during activity.
2. Improve your biomechanical control
Now your glutes are strong enough, let’s put the muscles to use. Improving your ability to control the tracking of your knee during loaded exercise reduces can reduce forces applied the ACL during risky manoeuvres such as stepping or speedy deceleration. This is best guided by a physio but even observing yourself stepping up or doing a singly leg squat can highlight some issues with the tracking of your knee.
3. Progressively practice risky situations in your sport
By practicing situations known to cause injury, starting at low speeds and increasing with time you improve your neuromuscular control and feel much more confident in these movements. For field athletes, this could take the shape of stepping around cones or deceleration drills. For those on the court, practicing jumping and landing on the one leg and stopping plus passing might be an idea.