Anterior Cruciate Ligament Injury

Injury to the cruciate ligament is a common but severe injury within the knee.

Where is the Anterior Cruciate Ligament (ACL)?

The ACL is located within the structure of the knee.

Knee ACL location 300x196

The knee joint is the largest joint in the body that allows the knee to flex and extend. Additionally, it has the ability to rotate and glide.

Knee full image 300x299


Ligaments connect the bones of the joint for stability and allow controlled movement. Ligaments on the inner and outer side of the knee (collateral ligaments) prevent the knee from bending inwards or outwards.

What does the Anterior Cruciate Ligament do?

Ligaments in the centre of the knee, called the cruciates, prevent excessive rotation of the knee.


Knee torn ACL diagram 300x183What causes an ACL to tear?

Typically the anterior cruciate ligament is torn when a severe injury occurs to the knee involving excessive twisting which ruptures part or all of the ligament.

The ACL Injury

Resulting Symptoms

Injury to the Anterior Cruciate Ligament results in

  • Increased forward movement and rotation of the leg bones relative to each other
  • Feeling of instability and excessive movement of the knee
  • Typically, significant bleeding into the knee will occur resulting in
    • increased swelling
    • pressure in the knee
    • increased pain
    • stiffness
    • immobility

Sudden changes in direction, twisting and rotating movements (rather than and walking and running) create more pronounced symptoms.

Other Knee Injuries

Injury to the ACL is often associated with other injuries to the knee such as damage to the cartilages (shock absorbers of the knee), the bearing surface of the knee, and other ligaments of the knee.

Resulting Mobility

Initially the knee is very painful, swollen and often you will be unable to walk without the use of crutches or support.

How is an ACL injury treated?


The main function of the Anterior Cruciate Ligament (“ACL”) is to prevent excessive movement of the knee. Strengthening the muscles about the knee that help control and stabilise the knee will partially help compensate for the damaged cruciate ligament.

If reconstruction of the ACL is necessary, physiotherapy supervision of your recovery programme is mandatory. The first focus is regaining movement, followed by a strengthening programme.

Anterior Cruciate Ligament Reconstruction

Anterior Cruciate Ligament Reconstruction surgery is a replacement of the torn ligaments.

Why is it necessary?

This ligament has no ability to heal when significantly damaged and so must be replaced with a new ligament (ligament graft).

When should it be done?

Reconstruction may be necessary when

  • Significant damage has occurred where the ligament is fully torn
  • The ligament is torn enough where physiotherapy would not be sufficient to strengthen the knee
  • The future demands on the knee from the patient will be too great

Knee ACL Injury 300x416

What’s involved?

  • Surgery involves an inspection of the inside of the knee by an arthroscopy (keyhole surgery)
  • The damaged ends of the ligament are removed.
  • Anchorage points are made for the new ligament.
  • The new ligament is obtained from a remote spot on the body such as one of the hamstring tendons or part of the patella ligament.
  • The new ligament is anchored with a secure fixation device.


More recently synthetic (LARS) ligament grafts have become available and may be used instead of your own tissue to reconstruct the ACL.

What to expect after reconstruction surgery

The following is typical for recovery after surgery though variations occur from patient to patient.

  • An accelerated rehabilitation program commences immediately
  • The knee is swollen for approximately a month
  • Full weight bearing is allowed immediately but crutches may be required for the first couple of days
  • You will require a physiotherapist to supervise your rehabilitation
  • Range of movement’ exercises are encouraged to regain the motion and increase as swelling subsides
  • It is necessary to avoid stretching the graft until it is firmly attached to the bone at approximately 3 months
  • The muscle strength of the knee is decreased for 9 to 12 months and competitive sporting activities are forbidden during this time.
  • Increasingly demanding knee exercises and activities are gradually introduced as your comfort and knee strength permit



If you would like to find out more about diagnosis and treatment of cruciate ligament injuries, please do not hesitate to get in touch with our rooms.


Download our information sheet to learn more about Anterior Cruciate Ligament Injuries and treatment options.