What is an ACL Tear? The Symptoms & Treatment Options

Written by Leon Mao
Physiotherapist, University of Melbourne
Medically reviewed by Dr Gina Arena
Research Fellow, University of Western Australia
Reviewed on March 29, 2022
Contributed by Jamie Page
Physiotherapist, Salford University

Man sitting on running track with knee pain from an ACL tear

According to the Medical Journal of Australia, Australia has one of the highest rates of anterior cruciate ligament (ACL) tear injuries, especially in younger individuals between 15-24 years of age.[1] In a 10 year study of elite level AFL players, 5% of all players experienced at least one ACL tear injury.[2]

ACL injuries are quickly becoming one of the most common knee injuries in Australia.[1] This is due to high levels of sports participation, especially at the elite level. As children begin to specialise in a particular sport at an earlier age, they are at a higher risk of ACL tears.[3]

Read on to understand what you should know about ACL tears; the risk factors, treatment options and expected recovery time.

What is an ACL Tear?

An ACL tear describes an injury to the anterior cruciate ligament. ACL tears range in severity, anywhere between a grade 1 (an overstretch injury) to grade 3 (a complete tear). As a result, people with this injury may experience knee pain, instability and swelling.

Grade 1: The ACL has sustained mild damage and may be stretched, but is still capable of providing stability to the knee joint.

Grade 2: The ACL has been stretched to the point where it is looser than normal and may have some partial tears of the ligament.

Grade 3: This is when the ACL is completely ruptured and is no longer providing any stability or support to the knee joint.

What are the symptoms of an ACL tear?

The symptoms of an ACL tear include an initial loud pop upon injury. This is followed by pain, rapid swelling, instability and a loss of range of motion. People may also experience a sense of giving way whenever they put weight on the knee.

Common symptoms of ACL tears

  • Sudden loud pop inside the knee followed by intense pain

  • Difficulty walking or weight-bearing

  • Swelling

  • Tenderness

  • Inability to strengthen the knee

  • An unstable feeling when standing on both feet.

What causes an ACL tear?

An ACL injury occurs when a sudden force hits the knee, usually when the foot is planted. This usually occurs during sports or in more physical workplaces like emergency services. The ACL can tear when changing direction rapidly, slowing down when running, or landing from a jump.

Common causes of ACL tears

  • Abrupt deceleration

  • Sudden change in direction

  • Overextending the knee

  • Awkward landing on flat-foot after a jump

  • Direct trauma (e.g. football tackle)

Sports that increase the risk of ACL tears

  • Football

  • Basketball

  • Soccer

  • Netball

  • Tennis

High-intensity sports that involve a sudden change in direction while running fast increase the risk of tearing the ACL.

How is an ACL tear diagnosed?

Anterior Cruciate Ligament tears can limit your sports participation and affect your ability to walk. It is best to have your condition diagnosed early by a medical professional to prevent further injury and start treatment as soon as possible.

There are several options available when it comes to diagnosing your knee pain as an ACL tear. One of the more common and most recommended by Australian GPs is an assessment from a physiotherapist.

Physiotherapists are rehabilitation experts when it comes to joint and ligament injuries. They are medically qualified to diagnose and treat ACL tears and other ligamentous injuries to manage your pain and help you recover fast.

Your visit with a physiotherapist will start with a simple consultation. Your physiotherapist will ask questions regarding the history of your injury. Use this time to discuss all your symptoms and issues related to your knee pain.

After establishing the background of your condition, your physiotherapist will then perform a detailed assessment of your knee structures and related muscles to determine the exact injured structures and eliminate other conditions.

The physiotherapist will then formulate a diagnosis and treatment plan based on your assessment. This whole process will take about 30 to 60 minutes.

If the physiotherapist believes that your injury is a Grade 3, or complete tear of the ACL, you may be referred to a surgeon for an opinion on whether surgery may be right for you.

You will also be given the details of your treatment program. This will include:

  • Number of treatment sessions

  • List of exercises you need to do at home

  • Strategies to manage the pain and prevent complications

  • Timeline of your recovery.

How is an ACL tear treated?

Anterior Cruciate Ligament tears can render your knee unstable and prevent you from doing activities that you love to do. Severe ACL tears can also lead to secondary complications if left untreated.

It is essential to seek treatment immediately as you feel signs and symptoms of an ACL injury to prevent further damage and start your recovery process as soon as possible.

There are several options when it comes to treating an ACL tear. One of the more common and the treatment option referred to by Australian GPs the most frequently is physiotherapy.

An ACL tear is a condition that physiotherapists come across regularly and the process of treating it is straightforward.

Treatment duration and progression will vary depending on the severity of your ACL tear.

Grade 1: Treatment of a Grade 1 ACL tear will focus on muscle strengthening, and recovery should be within a 6-8 week timeline. Surgery is not required in this scenario.

Grade 2: Treatment for a Grade 2 ACL tear with physiotherapy can take up to 3-4 months for recovery. The treatment protocol will actually be similar to the treatment for a Grade 1, except as there are more fibres that are torn, it will take longer for the body to heal. Your physiotherapist will match your treatment progression to your recovery so that there is little chance of re-injury.

In some cases where a Grade 2 ACL tear is not responding to conserative treatment, you may require surgery to assist in the process.

Grade 3: The most severe grade of ACL tears, is not surprisingly the most likely to require surgery. If surgery is required, rehabilitation can take anywhere from 6-12 months+.

Determining the need for surgery comes down to a few things:

  • Your age - the younger you are, the more likely you will need it fixed

  • How much pain you are in - if pain is unbearable, then surgery will be more likely

  • How active you are - the more sports and activities that you want to continue to be a part of, the more likely surgery will be.

If you do require physiotherapy, your treatment will focus on reducing the inflammation, improving your mobility and stabilising your knee joint through strengthening programs.

Depending on the severity of your ACL tear, a physiotherapist may provide you with a combination of the following types of treatments:

  • Range of Motion Exercises - Involves exercises that will keep your muscles active and preserve the range of motion of your knee.

  • Therapeutic Exercise - Includes exercise techniques to help you correct your body mechanics and improve overall function.

  • Stretching - Used to increase the range of motion of your knee joint and prevent stiffness.

  • Strengthening / Stabilisation Exercises - Includes exercise techniques used to strengthen the muscles and stabilise the knee joint.

  • Mobility Eexercises: Involves techniques to increase your range of motion and decrease joint stiffness.

  • Joint Mobilisation - Hands-on techniques designed to improve pain and decrease symptoms.

  • Dry Needling - Specialised technique used to relieve pain and reduce muscle spasms.

  • Soft Tissue Mobilisation - Used to stimulate muscle relaxation and improve blood circulation in the area.

  • Plyometric Exercises - Exercise programs given at the later stage of rehabilitation to help patients recover back to their pre-injured state.

Physiotherapy treatment can last for about 30 to 60 minutes. Most patients can feel the difference in just a single session.

Next step - Creating a treatment plan made for you

After your initial visit, your physiotherapist will create a detailed treatment program based on your condition and goals to help you achieve full recovery fast.

Self-care for an ACL tear

If you have an ACL tear, here are the best things you can do and avoid.

Things to do:

  • Protect

After the initial injury, protect your knee joint from further damage. Use assistive devices during walking and prevent unnecessary movement of your knee joint to control inflammation.

Wear your prescribed knee brace at all times.

  • Rest

Rest your body for a couple of days to prevent the worsening of your condition.

  • Ice

After the onset of your injury, apply a cold compress on the knee joint for at least 10 to 15 minutes every 2 hours to manage the swelling and pain.

  • Compression

Compressing the lower leg can effectively reduce the swelling and decrease the bleeding in the area of tissue damage.

  • Elevation

Elevation will also prevent swelling and facilitate a better flow of blood. Elevate your lower limb just above the level of the pelvis.

  • Optimal Loading

As signs of inflammation decrease, you can start gradually loading your lower body through assisted walking. Moving your ankles can also effectively decrease swelling and edema.

Things to avoid:

  • Avoid bending your knee in to pain

During the initial stage of your injury, avoid bending your knees to prevent further stress on your ACL.

Do I need a specialist or surgery?

Surgical intervention is the most common treatment option for a Grade 3 ACL tear. It is most common in younger adults who anticipate returning to sports or lots of activity. If a grade 3 tear occurs later in life, then surgery may not be advised.

An ACL reconstruction is an arthroscopic surgical procedure (keyhole). It involves removing the damaged/torn ACL and replacing it with a new and reliable piece of tissue to restore the stability in the knee.

The replacement ACL can come from one of three options.

  1. Autograft: This type of graft uses tissue from somewhere else in your body, most commonly, a portion of the hamstring tendon.

  2. Allograft: A graft that comes from a tissue donor.

  3. Synthetic graft: An artificial material replaces the tendon. This is less common as researchers are still working on finding the best and most reliable material.

What is the recovery time / prognosis for an ACL tear?

Ultimately, recovery time is dependent on proactively seeking professional treatment and the severity of your knee pain and injury.

Partial tears of the ACL are favourable and respond well with rehabilitation. It usually takes about 3 to 4 months to recover fully. With proper physiotherapy, athletes can gradually start playing again.

Complete tears that underwent ACL reconstruction could take over seven months to recover from. You will need to work closely with your physiotherapist to regain full range of motion of the knee and get back to the pre-injured state to play again.

Physiotherapy can significantly improve the outcome for ACL tears and help patients recover faster. Rehabilitation shows an increase in overall function and is one of the most significant predictors of complete recovery.

Recovery also depends on the following factors:

  • Age

  • Severity of injury

  • Other knee injuries

  • Compliance to treatment.

Can ACL tears be prevented?

Guaranteeing prevention can be impossible; however, you can decrease the risk of an ACL tear through some of these techniques. These preventative strategies listed are actually also useful tips for rehabilitation and recovery if you have already injured yourself.

  • Maintain flexibility: Maintaining the flexibility of your muscles through stretching will help you keep the natural range of motion of your knee joint. You can work on your glutes, hamstrings, quads and calf muscles in your stretching routine.

  • Strengthen your muscles: Keeping your lower body muscles strong by regular exercise will prevent soft tissue injuries and allow your joints’ greater stability. Strengthen your core, quads, hamstrings and glutes to improve overall control and stability in your lower body during intense activities.

  • Wear properly fitting shoes: Wear shoes that properly fit you and protect you from injuries. Ask your physiotherapist for a proper foot and lower body assessment for a recommendation of appropriate sports shoes.

  • Optimising your workouts and training routine: Over fatigued muscles provide less protection on your joints and increase the chance of injury. Make sure that you are adequately rested in between your activities.

Outlook and the main takeaways

An ACL tear is a common sports injury and should not be ignored. This injury can make your knees unstable and prevent you from participating in sports.

The key to preventing ACL injuries is optimised training and practice of preventive techniques to reduce the chance of injury. If you suspect that you have torn your ACL, get it seen immediately! Book a physio today!

Anatomy of the knee joint

Your knee joint is formed by the thigh bone (femur), shinbone (tibia) and kneecap (patella).

Different ligaments inside your knee keep it stable and control the amount of movement between the bones of your thigh and leg.

One of the most vital ligaments inside your knee is the ACL. It stabilises and controls the rotation and forward movement of the shinbone (tibia).

Excessive stress and sudden change in movements between the bones of your thigh and leg can cause tears in the ACL, causing pain and instability of the knee.

Written by Leon Mao
Physiotherapist, University of Melbourne
Published on March 29, 2022
Medically reviewed by Dr Gina Arena
Research Fellow, University of Western Australia
Reviewed on March 29, 2022
Contributed by Jamie Page
Physiotherapist, Salford University
Medical reviewers
Last medically reviewed on March 29, 2022
BookPhysio.com has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.
  • 1.

    Zbrojkiewicz D, Vertullo C, Grayson JE. Increasing rates of anterior cruciate ligament reconstruction in young Australians, 2000–2015. MJA 2018 [cited 2022 Mar 4];208(8):354-8.

  • 2.

    Liptak MG, & Angel KR. Return to Play and Player Performance After Anterior Cruciate Ligament Injury in Elite Australian Rules Football Players. Orth Jprt Med, 2017 [cited 2022 Mar 4]; 5(6).

  • 3.

    Field AE, TepoltF A, YangDS, & Kocher MS. Injury Risk Associated With Sports Specialization and Activity Volume in Youth. OrthJ Sprt Med, 2019 [cited 2022 Mar 4];7(9).

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