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ACL injury to the knee

Within the knee joint, there are four ligaments that support and limit the movement about the knee, and these can be injured through sport and trauma.  Ligaments are strong bands of fibrous connective tissue that connect bone to bone.  The ligaments about the knee joint are the:

  • Anterior Cruciate Ligament (ACL) which controls rotation and forward movement of the tibia (shin bone);
  • Medial Collateral Ligament (MCL) which provides stability to the inner side of the knee;
  • Lateral Collateral Ligament (LCL) which provides stability to the outer side of the knee; and
  • Posterior Cruciate Ligament (PCL) which controls backward movement of the tibia (shin bone). 

The ACL can be injured by over stretching the ligament or by a partial or complete tear.  The most common ways in which the ACL is injured is through:

  • Quickly changing direction, stopping, or moving while running, jumping, or turning.
  • A direct impact to the side of the knee for example in a Rugby tackle.
  • Over extending the knee.

Initial symptoms of an ACL injury include a ‘popping’ sound, swelling within the first six hours and pain especially when placing weight through the leg.  Initial treatment includes resting the knee, elevation of the knee, regular icing of the knee and non-steroidal anti-inflammatory medication.  Crutches may assist with walking in the initial stages after an ACL injury.

Diagnosis of an ACL injury is through a history and examination of the knee joint.  On examination there are certain tests that can be performed to determine ACL instability.  Your specialist may also send you for an MRI scan to confirm an ACL injury and determine whether any other structures of the knee were also injured.

The swelling and pain around the knee will usually start to settle over the coming weeks after an ACL injury.  It is at about this time that patients may start to experience a feeling of their knee giving way or instability about the knee.  At this stage physiotherapy may be of benefit to assist in regaining strength, range of movement, proprioception, balance and function.

Reconstruction of a ruptured ACL is not indicated in all patients.  A reconstruction may be indicated in patients who have a continued feeling of their knee giving way, who would like to continue to be involved in sports requiring pivoting, or patients who perform squatting and heavy manual work in their job.  If you are not involved in sports or perform heavy manual work then you may not require reconstructive surgery. 

Making the decision to proceed to an ACL reconstruction is a collaborative one between the patient and orthopaedic surgeon, Dr Prodger.  The patient is able to make an informed choice to proceed following a thorough discussion of the benefits of surgery and the risks of surgery.