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Anterior Cruciate Ligament Tear (ACL Tear)


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 e.g. during tackling in football, pivoting or landing from a jump.


What is the Anterior Cruciate Ligament (ACL)?

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.

What are the common causes?

The ACL is commonly injured when there is an excessive strain on the ligament by:

  • 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

What are the signs & 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

What are the risk factors?


  • Athletes engaging in sports that require a lot of cutting and/or pivoting e.g. basketball, soccer, rugby


  • 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 at a bio-mechanical disadvantage.

Poor strength and conditioning

  • You may be "unfit" for certain sports which have a higher demand for your body strength and conditioning


  • Uneven exercise terrain or wet exercise surface due to poor weather may increase the chance of ACL injury

What types of 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. First line treatment is to go for conservative management in order to achieve the following goals:


  • The above goals are achieved using a range of physiotherapy treatments including electrophysical agents and exercise therapy. Treatment is progressed over a period of 3-6 months, and improvements are unique to each individual, depending on severity of the injury. Compliance with the home exercise program 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
  • Following the surgery, you will be encouraged to undergo 6-9 months of physiotherapy before returning to your sports activities

What can I do to help myself?

Do's Dont's
  • protect your knee by wearing your knee brace especially when you still experience buckling or give way
Return to any sporting activity when you still have weakness in muscles
Relative Rest
  • rest from sports and avoid cutting or pivoting
Change or add new exercises to your home exercise program without discussing with your physiotherapist
  • 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


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 3 months
    • Commence light sports training at 6 months
    • Commence competitive sports at 9 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 to 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


- Last updated 7 Oct 2011,4:49 pm

The content of this website is provided for general informational purposes only and is not intended as, nor should it be considered a substitute for, professional medical advice. Do not use the information on this website for diagnosing or treating any medical or health condition. If you have or suspect you have a medical problem, promptly contact your professional healthcare provider.

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