Anterior Cruciate Ligament tear

The Anterior Cruciate Ligament is an important ligament which is found in the middle of your knee joint. Its purpose is to keep your knee stable, especially when doing movements like running quickly in different directions.


An anterior cruciate ligament tear can make your knee feel loose or unstable and that it may give way .

Download pdf patient information guide for ACL reconstruction surgery

At the time of an anterior cruciate ligament tear you may notice:

– A sudden “popping” which may both felt and heard in the knee.
– Swelling of the knee within minutes to hours of the injury – caused by bleeding into the knee joint
– Moderate to severe pain in the knee

Symptoms that may occur days to weeks after the injury include:

– Giving way: After the swelling improves you may feel a sense of ‘instability’ in the injured knee. This means the knee moves around too much and may lead to the knee giving way. This is often felt during activities such as squating, walking down stairs, pivoting on the knee or stepping sideways.
– Ongoing knee pain
– Ongoing swelling (usually less severe than at the time of injury)

If you experience any of the symptoms of ACL injury it is important to see either a physiotherapist or doctor for assessment. Generally the longer you take to seek treatment the longer it will take to recover and increased risk of irreversible damage..

A tear in your ACL usually occurs when playing sport. Occasions when it is common is when you slow down very suddenly to change your direction or come into forcefull contact with another sportsperson. Some sports have a high associationwith an ACL tear such as football, netball, basketball, martial arts and gymnastics. This is because they involve jumping, running with sharp turns, quick stops, pivoting and forcefull contact.

Women have a much higher risk of having an ACL tear than men when doing the same sports because women tend to have imbalanced thigh muscles. Due to multiple factors the muscles at the front of the leg tend to be unproportionately stronger than the muscles at the back of the leg in women. This strain also puts an ACL reconstruction at more risk of a rerupture and is factored into rehabilitation.


Your doctor or physiotherapist will thoroughly examine your knee in a variety of positions before ordering tests.

They may order x-rays or magnetic resonance imaging (MRI) scan. X-raysdemonstrate a bone injury (e.g. fracture) or leg alignment problems. An MRI scan creates an image of the soft tissues of your knee enabling visualisation of the ACL, PCL, menisci and cartilage among others to assess injury.

It is important to remember that any imaging is an aid for diagnosis in combination with clinical history and examination. An important old saying is that you treat the patient not the scan!

Associated Injuries

There are several associated injuries that can occur when the anterior cruciate ligament tears;

Meniscal Tears: As the ACL and meniscus are both structures in your knee which are close, if you injure one you may have injured the other. An injured meniscus can increase the risk of joint problems later on.


Arthritis: It is common to damage the cartilage lining of your knee joint by the forces required to tear the anterior cruciate ligament.This results in progressive cartilage damage over time leaving it deficient causing arthritis. About half the people with an ACL tear develop osteoarthritis in the involved joint 10 to 20 years later. Arthritis may occur despite having surgery to reconstruct the ligament.
Other ligament tears: Occasionally other ligaments such as the medial and lateral collateral or posterior cruciate ligaments can be torn as well. This is a complex problem and requires individualised management. These have a greater risk of ongoing problems and earlier development of arthritis.



The aims of treatment for an ACL injury are to reduce pain and swelling in your knee, restore the normal joint movement and strengthening the muscles around your knee.

There are many options which are available for you

Short term

To treat the immediate injury:

1. Use RICE (rest, ice, compression, elevation)
2. Take pain relievers such as paracetamol as needed
3. You can use an elastic bandage around your knee
4. Use a splint or walk with crutches if needed

Anterior cruciate ligament reconstruction

To surgically repair your ligament, a piece of tendon from another part of your leg is used to replace it.

Surgery may be an option if:

You are unable to continue doing your normal activities because of knee symptoms
You’re very active and want to continue doing heavy work, sports or other recreational activities. However, sometimes this may not be practical.
Other parts of your knee like the meniscus or other ligaments, are also injured

ACL surgery is a procedure using arthroscopic techniques. This means the surgeon puts a small instrument (arthroscope) with a light and a small camera into your knee via small incisions. This allows your surgeon to see the inside of your knee joint and repair your ACL.

Anterior cruciate ligament reconstruction rehabilitation

ACL reconstruction rehabilitation is best broken down into 5 phases.

For each phase there is a list of goals and outcome measures that need to be achieved before moving onto the next one.

This will be under the guidance of your Physiotherapist.

The five phases are:

Phase 1: Recovery from surgery
Phase 2: Strength & neuromuscular control
Phase 3: Running, agility, and landings
Phase 4: Return to sport
Phase 5: Prevention of re-injury

Important things to focus on during rehab

1. Get the knee straight first (within the first 2-3 weeks) and maintain. Then work on Flexion.
2. Use your body as a guide. If knee pain or swelling is increasing then the knee isn’t tolerating what you’re doing to it so go back a step and discuss with your physiotherapist.
3. Technique is everything. Exercises done incorrectly can damage your reconstruction.
Return to high impact forces slowly following each phase.
3. FINISH your ACL rehabilitation.

A painless stable knee often starts from phase 2 but your rehabilitation is barely a 1/3 the way. Your reconstructed ACL has no nerves to tell you when are putting it at risk of rerupture.

Nonsurgical rehabilitation

Sometimes surgery may not be necessary and the doctor will discuss the options with you.
This may be an appropriate choice for you as long as long as you’re willing to give up activities that place extra stress on your knee. You may want to consider rehabilitation alone if:

You only have a partial tear of your ACL
You don’t do sports that involve quick turning, pivoting or jumping. Or if you aren’t very active
You already have advanced knee arthritis


Prevention is better than reconstruction! There are a few steps you can take to decrease the chance of getting an ACL injury:

Firstly use correct sporting technique: Learning how to safely do actions in your sport like jumping or quick turning are easy ways to prevent injury. There may be protective sporting equipment designed for your sport may be an option.
– Condition yourself: Many high performing athletes reduce their risk of ACL injury doing training drills. These routines incorporate things like agility, balance and power to help teach the muscle to react properly.
– Hamstring strengthening (especially for women): As women are at a higher risk of ACL injury they should take care to strengthen and stretch their muscles.
– Maintain fitness: If you’re on a seasonal sports team, stay active and fit throughtout the year. This helps prevent you getting injured when your season starts.

Contrary to popular belief, using a knee brace during sports doesn’t reduce your risk of injury. It only provides a false sense of security.

How long will it take to return to sports?

Everyone recovers at a different rate. The most standard answer that you will hear from a doctor is six to twelve months. It’s possible to return sooner than 12 months, but the risks for re-injury are higher. It takes about 12-18 months for your new ACL to be in peak condition. At 12 months the graftis about 80 – 85% strong, this is considered sufficient by ost surgeons to return to sports provided you have successfully completed full rehabilitation.

Remember your reconstructed ACL graft does not have any nerves, if you return to sport too early, you will not be able to feel if you are putting it at risk until it ruptures!

Will I need surgery?

It depends. ACL tears can be partial or complete. With stretching and strengthening exercises and a good knee brace, it is possible to live with a tear. If you find you can not lead the life you wish and are unwilling to modify it, then surgery is for you. “Modify your life to fit your knee or modify your knee to fit your life” is the standard quote. However, surgery is frequently recommended for very active patients, particularly those involved in sports due to the associated irreversible injuries that can occur with repeated instability episodes..