ACL Tears – The What, The Why and The How

ACL Tears

Tearing or spraining your ACL can be excruciating and debilitating, and the recovery from ACL tears can take months and may even require surgery.

One of our qualified Inline Physio clinicians, Jacob Hurley, has had plenty of experience with this kind of injury, unfortunately experiencing three (3) ACL ruptures in his lifetime.

He’s put together this blog which outlines a bit more about the what, the why and the how of ACL tears.

What is ACL injury?

The anterior cruciate ligament (ACL) is a band of dense tissue, known as a ligament, which connects the shin bone to the thigh bone on an inward angle.  It’s this angle and positioning of the ligament that prevents inward rotation of the knee.

The ACL is often injured in field-based sports which require very quick jumping, twisting and pivoting such as: AFL, basketball, rugby, soccer, netball and downhill skiing.

ACL injuries can range in severity – from a stretched ligament (grade 1 sprain) to a full tear or rupture of the tissue (grade 3 sprain).

An ACL injury can be caused by direct contact, for example a collision with an opposing player. However, non-contact injuries to the ACL are actually far more common. (We explain more about this below.)

Many other structures in the knee can also be injured at the same time as an ACL tear.

A common presentation is an ACL tear which also features bone bruising, a sprain to the medial collateral ligament (MCL or inner knee ligament), and meniscus tear/s.

ACL Injury Causes: Direct and Indirect Contact

The most common injury to the ACL ligament is unfortunately a full rupture, which may or may not require surgery.

There are two types of mechanisms of injury:

  1. Direct contact which contributes to approximately 30% of injuries, and
  2. Non-contact which contributes to about 70% of injuries.

Indirect Contact ACL injury

The most common scenario is a non-contact ACL tear, where the athlete attempts to transfer too much rotational force through the knee.

This can occur with a cut-and-plant movement, with a sudden change of direction and where the heel is rapidly planted into the ground.

These sudden actions cause significant inward rotation of the knee and can lead to the ligament failing and rupturing.

Direct Contact ACL Injury

There are of course other scenarios in which the ACL can tear, such as a direct contact blow to the knee by an opposing player or object (Particularly when the leg is planted, and the foot is stuck in the ground).

Why do ACL injuries occur?

As the frequency of ACL tears progressively increases as the years go by, we are learning more about why they happen.

The why can be split into two factors: controllable risk factors and unmodifiable risk factors.

ACL Injury Risk Factors: The unmodifiable

ACL tears are more common in females (between 2.4 and 9.7 times) due to biomechanical differences – namely the inward angle and rotation of female’s hips and their higher ligament laxity.

Other unmodifiable risks include:

  • Certain bony structures are now being seen to increase the likelihood of a ligament injury, as well as having a family history.
  • Turf and field conditions have also been suggested to contribute to increased chance of injury.
  • Type of shoe and the amount of grip that this shoe has on the ground. Surprisingly, the less grip to the ground the better. This means that longer and wider studs, traditionally used to increase grip into ground, may increase the risk of these injuries.

ACL Injury Risk Factors: The modifiable:

  • Decreased strength in the muscles which control knee stability is also more common in females; however, this is a controllable risk factor.
  • Dynamic stability, balance and control in the hip, knee and ankle are contributing factors.
  • Body mass (weight) will also increase the amount of force required on the knee.

Would you like to learn more about ACL injury symptoms and treatments? Have a read of our blog about ACL injury treatment here.

Treating ACL Tears

If you have injured your knee and suspect that you’ve torn your ACL, please see a qualified physician or physiotherapist for a proper assessment.

Our Brisbane team has plenty of experience diagnosing and treating ACL ruptures, so if you’d like their help, please don’t hesitate to make a booking here.