The Anterior Cruciate Ligament (ACL) is one of 4 main ligaments within the knee and the most commonly injured. There are 2 main ligaments in the middle of the knee which form an ‘X’, one of these being the ACL. It is a band of strong, fibrous tissue that connects the bottom of the femur (thigh bone) to the tibia (shin bone).

The main purpose of this ligament is to restrict movement within the knee, in particular, anterior tibial translation (shin shifting forward) and internal tibial translation (shin rotating inwards). That is why it is most important in supporting the knee and rotational type movements such as pivoting.

How is the ACL injured?

70% of anterior cruciate ligament injuries are non-contact and generally occur when the knee rotates inwards and can be during movements such as:

  • Changing direction
  • Pivoting with the foot planted firmly on the ground
  • Landing awkwardly from a jump
  • Stopping suddenly

It is quite common for other structures in the knee to be injured along with the ACL. The medial meniscus and medial collateral ligament (MCL) are at the greatest risk of injury, along with bone bruising.

Who is at most risk of injury?

ACL injuries are most common in: 

  • Males aged 19-25 years old
  • Females aged 15-19 years old
  • There are increasing numbers in children aged 5-14 years old
  • Those participating in pivoting sports such as AFL, soccer, netball
  • Females are at a greater risk of injury than males

How do I know if I have injured my ACL?

Everyone has a different experience with this injury, however, signs and symptoms may include:

  • A loud ‘pop’ sensation
  • Pain and difficulty putting weight through the leg
  • A feeling of ‘instability’ or giving way of the knee when walking
  • Early onset of swelling and loss of movement in the knee

What should I do if I think I have injured my anterior cruciate ligament?

As with any other traumatic injury, it is important to follow the RICE principle initially. This includes resting, icing, compression, and elevation. Crutches may be used to help with walking, especially if there is pain, swelling, and instability causing difficulty with moving around. The person should then make an appointment as soon as possible to see their GP, sports doctor, or physiotherapist to assess the injury.

How is an ACL injury diagnosed?

Your physiotherapist or doctor will be able to assess your injury based on the history of how the injury occurred along with some physical tests to feel how much movement there is in the knee. If these tests are positive, you will then be referred for an MRI to confirm injury to the ACL. If the MRI confirms that the ACL has been ruptured or there are any other injuries, you will then be referred to an orthopaedic surgeon to discuss your options for treatment.

Will I need surgery for my knee injury?

Not everyone who injures their ACL needs surgery. Athletes can return to high-level sports and physical activity without the need for surgery and studies have shown no differences in knee osteoarthritis in patients who had an anterior cruciate ligament reconstruction and those who did not (Harris et al. 2015).

There are a number of factors to weigh up to determine whether one does or does not need ACL reconstruction surgery. A screening system is used to classify those that may be potential ‘copers’ and be able to manage without a new ACL and the ‘non-copers’ who should follow the surgical pathway sooner.

A ‘coper’ is someone who is:

  • Is able to return to jumping/cutting/pivoting activities without any instability or ‘giving way’ of the knee
  • Does not plan on returning to a pivoting sport such as AFL, netball, soccer
  • Does not notice ‘giving way’ or instability within the knee
  • Does not have any other associated common knee injuries

A ‘non-coper’ is someone who:

  • Experiences ‘giving-way’ or instability of the knee when returning to pre-injury activities
  • Has not regained a normal walking pattern within 4 months
  • Has other associated knee injuries (i.e. meniscus, other ligament injuries)

The best available research shows that all patients should start with conservative management including physiotherapy and exercise before deciding whether they do need surgery (Smith et al. 2014).

What is involved in ACL reconstruction surgery?

The aim of ACL surgery is to ‘reconstruct’ a new ligament in place of where your ACL used to be. This can be done by using either a:

  • Hamstring graft
  • Patellar tendon graft
  • LARS (synthetic)
  • Allograft (from donor)

Hamstring grafts are the most common procedure in Australia. This involves the removal of one or two hamstring tendons, which are then folded over each other to create a ‘new’ ACL, which is then attached inside the knee to create stability within the knee joint. 

How can physiotherapy help?

Physiotherapy is important from as soon as the injury has occurred. In the initial acute stages of injury, your physiotherapist will be able to help you with:

  • Assessing the knee and organising a referral for a scan or to a sports doctor
  • Decreasing pain and swelling and helping you to start walking normally again 
  • Education and support around rehabilitation, options for operative vs non-operative management, and return to work and sport

Along with the guidance of an orthopaedic surgeon, we will work out whether or not surgery is the best treatment option for you. 


If you choose ACL reconstructive surgery, it is important to have an appropriate ‘pre-habilitation’ plan in place from your physiotherapist leading up to surgery. 

There is great evidence to show that doing 10 sessions of heavy strength and neuromuscular training over a 5 week period before an ACL reconstruction can result in:

  • Improved knee function
  • Improved quality of life
  • A greater likelihood of returning to pre-injury levels of sport 

Before going into surgery you want to make sure you have:

  • Full movement of your knee (i.e. can completely straight and bend the knee)
  • Minimal to no swelling
  • Normal walking pattern (i.e. not limping)
  • Good balance
  • Strong thigh muscles 
  • Generally strong overall


Your physiotherapist will see you one week after your ACL surgery and start to build on your exercise and rehabilitation program. The general goals to achieve at each phase are as below.

Stage 1 (Weeks 0-6):

  • Reduce pain and swelling
  • Regain normal range of knee flexion and extension range of movement
  • Gradually return to a normal walking pattern
  • Start strengthening the quadriceps, hamstrings, gluteals and calves as soon as possible

Stage 2 (Weeks 6-12):

  • Progress exercise program to a weighted gym based program
  • Full knee range of motion in weight-bearing – i.e. full knee flexion and squatting range of motion
  • Build on single leg control and stability

Stage 3 (3-6 months):

  • Regain full strength and endurance in hamstrings, quadriceps and surrounding muscles that are within 10% of the non-operated leg.
  • Continue to increase weights with gym program
  • Introduce straight line jogging, with a rehabilitation program to build on speed and distance
  • Start loading the knee in full extension
  • Start hopping, jumping and side-hopping drills
  • Challenge stability of the knee with exercises on uneven surfaces

Stage 4 (6-8 months):

  • Progress running intensity up to 100%
  • Cardiovascular and weight program to return to ‘pre-injury’ levels
  • Challenge single leg exercises
  • Start to add in more side-to-side movements and change of direction drills
  • Progress power training

Stage 5 (8-12 months)

  • Return to team training
  • Increase intensity of agility/change of direction drills
  • Full return to competitive work leading into return to sport
  • Final return to sport testing by physiotherapist for clearance to play

Conservative management

If you choose not to have an ACL reconstruction, your physiotherapist will still follow the same milestone-based guideline as above, however, the time before returning to sport is generally reduced.

How often will I need to see my physiotherapist post-surgery?

The first 6-8 weeks post-surgery, your physiotherapist will likely see you 1-2 times per week, depending on your progress. After this, your appointments will then start to decrease to fortnightly and then monthly, as your ACL rehabilitation will be based on testing and exercise programs.

When can I return to sport?

As there is such a high risk of re-injuring the reconstructed ACL or the ACL in the other leg, return to sport after ACL injury is milestone-based rather than based on a particular time frame. This is generally around the 12-month mark. For every one-month delay in return to sport 9 months after ACL reconstructive surgery, the risk of re-injury is reduced by 51%.

Before returning to sport each athlete must pass a number of tests including:

  • Hamstring and quadricep strength within 10% of each leg
  • A number of different hop tests, with no more than 10% difference between sides
  • Single leg control testing such as single leg squats, with the ability to demonstrate good control 
  • Agility testing
  • Psychological readiness using a number of different questionnaires 
  • Clearance from the orthopaedic surgeon 

How can I prevent ACL injuries?

ACL injuries can be reduced by 50% by performing a 30 minute exercise prevention program each week. This 30 minutes can be broken down into 3 x 10 minute sessions.

There are specific rehabilitation programs available for AFL, soccer, and netball. They are:

  • AFL Footy First
  • FIFA 11+
  • Netball Knee

Not only do these types of programs reduce the risk of injury, but ankle injuries are reduced by 40% and all lower limb injuries decline by 22%. They have also been shown to improve:

  • Balance
  • Jumping
  • Power
  • Agility 
  • Speed

This is especially important for those athletes at higher risk of ACL injury. These individuals are:

  • 14-18 year olds and males 19-25 year old 
  • Players with a past history of injury 
  • Those with a family history of anterior cruciate ligament rupture (mother or father) 
  • Female athletes 
  • Athletes with current or a past history of knee pain 

Physiotherapy for anterior cruciate ligament injury and common knee injuries

The initial assessment with a physiotherapist will usually begin with a discussion of your pain symptoms, the specifics of which can influence everything from treatment to management. Take some time to explain what each part of your body is doing better or worse than before you started treatments; for example, are these issues worse when you’re stressed at work? Which activities have made your pain worse and which have made it go away? This information will be essential in determining a plan of action to get you back on your feet!

Physiotherapy can help you understand your condition and to achieve optimal physical health. Our physios will work with you one-on-one with both hands-on therapy and practical testing to find the cause of your pain. We will also keep track of how things are changing so that we can continue to improve and make sure you’re always getting the best care possible!


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