Anterior Cruciate Ligament Tear (ACL Tear)

What you need to know about a torn anterior cruciate ligament (ACL), its symptoms and treatment.

What Is the Anterior Cruciate Ligament (ACL)?

The anterior cruciate ligament, also called the ACL, is one of the four major ligaments of the knee helping to prevent excessive motion of the knee joint. It is commonly injured during sporting activities , for example during tackling in football, and pivoting or landing from a jump.

The ACL is an important structure that joins the thigh bone (femur) to the shin bone (tibia). It prevents the shin bone from moving forward excessively under the thigh bone.

Related: Aches and Pains

What Are the Common Causes of ACL Injury?

The ACL is commonly injured when there is an excessive strain on the ligament from: 
Direct trauma — direct blow to the side/behind the knee
Pivoting  — twisting of the femur while the tibia is still stationary e.g. sudden change of direction while running
Hyperextension (overextension) —  this usually happens when landing from a jump 

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ACL Tear Signs and Symptoms

A tear of the ACL is usually accompanied by: 
A "POP" sound 
Intense pain 
Immediate swelling 
Inability to put weight on injured leg
"Giving way" of the knee 

Following an ACL injury, you may experience: 
Pain and swelling
Loss in range of movement
Knee instability

Related: Knee Arthritis

What Are the Risk Factors of an ACL Tear?

Sports — athletes engaging in sports that require a lot of cutting and/or pivoting e.g. basketball, soccer, rugby.
Gender — women are significantly more at risk than men as they tend to have greater thigh muscle imbalances due to weaker hamstrings compared to their quadriceps. Women also have a greater Q-angle of the patella, also known as knee cap, (which places the knee in a more 'inward' position), and therefore are at a bio-mechanical disadvantage.
Poor strength and conditioning — you may be "unfit" for certain sports which have a higher demand for body strength and conditioning.
Environmental — uneven exercise terrain or a wet exercise surface due to poor weather may increase the chance of an ACL injury.

What Types of ACL Treatment are Available?

An ACL injury will result in knee instability and buckling. This is due to knee muscles weakening secondary to pain or muscle disuse. The first-line treatment is to go for conservative management in order to achieve the following goals:
Reduce knee pain and swelling
Increase range of knee movement
Increase muscle strength
Increase stability of the knee 


The above goals are achieved using a range of physiotherapy treatments, including electrophysical agents and exercise therapy. Treatment is progressed over a period of three to six months, and improvements are unique to each individual, depending on the severity of the injury. Compliance with the home exercise programme prescribed is necessary to enable an early return to sports. 

There is a possibility that following a period of conservative management, the knee may still buckle or give way. This usually occurs in contact sports such as soccer or rugby. Failure to respond successfully to conservative management may indicate the need for ACL reconstruction surgery.


ACL reconstruction surgery involves replacing the torn ACL with a graft taken from a tendon around the knee.

Commonly-harvested tendons are the patella tendon and the hamstring tendon. The graft is then attached to run in a similar direction as the ACL.

What Can I Do to Help Myself?


Protect your knee by wearing your knee brace especially when you still experience buckling or give way 
Rest from sports and avoid cutting or pivoting 
Ice your knee whenever possible and after doing your exercises 
Apply compression bandage to reduce swelling 
Elevate your leg while resting or sleeping to reduce swelling 
Strengthen your muscles as instructed by your physiotherapist  
Inform your physiotherapist if you have any knee pain or swelling after exercises  


Return to any sporting activity when you still have weakness in muscles
Change or add new exercises to your home exercise programme without discussing with your physiotherapist  

Related: KneeBuddy App

Frequently Asked Questions

1. What can I expect after my surgery?

There are some milestones that can be achieved as your rehabilitation progresses. They are:
Commence jogging at three months
Commence light sports training at six months
Commence competitive sports at nine months

Don’t be disappointed if you do not reach these milestones at the given time frame. Continue to work at it! Your ability to return to sports depends on your commitment to the exercises given. Your doctor and physiotherapist will also clarify any restrictions on sports participation based on the outcome of your surgery and the progress of your rehabilitation.

2. How is progress charted and how is it determined if you can return to sports? 

Progress is measured with:
Graft integrity testing 
Strength testing
Questionnaire to determine knee function

Following the surgery, you will be encouraged to undergo six to nine months of physiotherapy before returning to your sports activities.

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