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Understanding ACL injuries

Dec 7, 2023 | Injury, Knee

Injuries to the anterior cruciate ligament (ACL) are common but they can have profound implications for joint stability and overall wellbeing.

What is the ACL?

The ACL is one of the four major ligaments that stabilise your knee joint.

Though it can twist a little, your knee is a hinge joint that’s meant to bend (flex) and straighten (extend). Muscles and ligaments – like the ACL – prevent it moving from side to side and create stability. The ACL stops your femur (thigh bone) from moving forward over your knee.

The ACL runs diagonally in the middle of the knee, connecting the femur (thigh bone) to the tibia (shin bone). The primary function of the ACL is to control and limit excessive motion of the knee joint, particularly rotational movements.

How does the ACL get injured?

The ACL sustains an injury when it twists at speed or under force in sudden stops, pivots or jumps. Just ask Sam Docherty, Ellie Carpenter or Tayla Curtis.

The most common way is when you plant your foot and pivot. That can often happen during sports such as Australian Rules Football (AFL), soccer, rugby, skiing or netball due to the dynamic and often unpredictable movements involved. About 70% of all ACL injuries are non-contact but the ACL can also be injured during a collision on or off the sports field.

What makes you vulnerable to an ACL injury?

Beyond your choice of sport, risk factors for an ACL injury include:

  • Being female – factors such as size, pelvis shape and ligament laxity make women 3 times more likely than men to experience an ACL injury.
  • Your biomechanics – as most ACL injuries occur without contact, it’s likely that the biomechanics of your trunk, hips, knees and ankles play a role.
  • Faulty movement patterns, like moving your knees inward when squatting.
  • The level of friction between your footwear and the playing surface.

Some factors can make you more vulnerable to an ACL injury, including:

  • Muscle weakness or imbalance.
  • Genetic factors.

How do you know if you’ve injured your ACL?

Trust me, you’ll know! A torn ACL hurts…a lot!

Signs and symptoms of an ACL injury include:

  • Severe pain and inability to continue your activity.
  • A popping sensation in the knee – you may even hear this.
  • Rapid swelling.
  • Feeling like your knee is giving way when you try to stand.
  • Losing mobility in the knee.

If you injure your ACL during a game, you’ll probably find you can’t continue playing. After the initial injury subsides, you may find you’re able to limp around but that you don’t trust your knee because it keeps giving way. That persistent instability and the resulting loss of confidence affects your ability to return to normal activities.

Learn more about ACL injury management


Treatment depends on the extent of your injury and importantly, your lifestyle.

Physiotherapy usually plays a key role, both as a treatment in its own right and as part of surgical prehab or rehab.

To repair your ACL, your surgeon takes a small graft and inserts this in place of your torn ACL. The graft may come from a donor but more commonly comes from your own body – we may use your hamstring, patella tendon or quadriceps tendon, for example.

Learn more about ACL reconstruction

Can you prevent an ACL injury?

Preventive strategies to reduce the rate of ACL injuries include:

  • Improving neuromuscular conditioning and muscular reactions through training drills requiring balance, power and agility alongside plyometric exercises such as jumping.
  • ACL conditioning programs – often recommended for female players.
  • At least 4 weeks of pre-season training.
  • Following best practice recommendations regarding warming up, cooling down and recovery time between workouts.

Some prevention programs have been shown to reduce ACL injury by 67%.

How can I help?

If you’ve injured your ACL, please contact our office to make an appointment,. We are here to investigate your discomfort so you  can get back to the life you enjoy.

I am an orthopaedic surgeon with extended expertise in all aspects of knee surgery including:

  • ACL reconstruction.
  • Robotic knee replacement.
  • Multi-ligament knee reconstruction – complex procedures for patients who have sustained several different knee injuries at once.
  • Limb realignment.

I perform ACL reconstruction as an arthroscopic (keyhole) procedure. This is minimally invasive surgery, allowing for smaller incisions which means less scarring, less post-operative pain and faster rehabilitation.

If you’d like to improve your knee stability so that you can move with confidence again, please make an appointment today.