Anterior Cruciate Ligament

 Anterior Cruciate Ligament Anatomy

 Anterior Cruciate Ligament
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All bones are connected to other bones through ligaments. The thighbone (femur), shinbone (tibia), and the kneecap (patella) all meet to form the knee joint. In addition, you can find four primary ligaments that provide support, acting like strong ropes which helps to connect the bones together and keep your knee stable.

 Anterior Cruciate Ligament torn knee
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 Anterior Cruciate Ligament differences

Collateral Ligaments

These ligaments are found on the side of your knee and help to prevent your knees from bending unnaturally. They are also responsible for the sideways motion of your knee. On the outside of the knee, there is a lateral collateral ligament and on the inside of the knee, there is the medial collateral ligament.

Cruciate Ligaments

These are the ligaments that are inside your knee joint and they cross over each other and form an X. The anterior cruciate ligament is in the front and the posterior cruciate ligament is in the back. Therefore, if you were to look at them straight on from the kneecap, you would see the anterior cruciate ligament in the front.

The ACL runs diagonally in the middle of the knee. It prevents the tibia from sliding out in front of the femur, as well as provides rotational stability to the knee.

Description of  Anterior Cruciate Ligament

These ligaments help to provide rotational stability, as well as control the back-and-forth movement of your knee. The anterior cruciate ligament is located in the middle of the knee, and it helps to prevent the tibia from sliding in front of the femur bone.

The anterior cruciate ligament is usually injured with other parts of the knee such as ligamentscartilage or meniscus. When you injure ligaments it is considered a ‘sprain’, and the severity of the sprain depends on various things.

“Sprains” are graded on a severity scale.

Grade 1 Sprains: The ligament has been stretched slightly and only mild damage has occurred. The ligaments are still capable of keeping the knee joint stable.

Grade 2 Sprains: The ligament has stretched too far and has become loose. Medically this is referred to as a partial tear of the ligament and is very rare. Most anterior cruciate ligament injuries fall into the grade 3 category.

Grade 3 Sprains: This is when the ligament has been completely torn and has been split into two. At this point, the knee joint is no longer stable.

Cause of ACL Injuries 

As mentioned before, it is very common for athletes who are involved in extreme sports to tear their anterior cruciate ligament. However, studies have shown that women are more prone to this type of injury than men are. This is likely due to the difference in muscular strength, physical fitness, and neuromuscular control. However, it has been proposed that estrogen and how it affects ligament properties, may also play a part in the increased injury. In addition, a woman’s pelvis and leg alignments may contribute to the issue as well.

Female or male, injury can occur in a few different ways including:

– Sudden change in direction

– Coming to a complete stop quickly

– Incorrect landing after a jump

– Direct impact with another person or object


When you injure your anterior cruciate ligament, you may hear a “popping” noise and you may feel your knee give out from under you. Other typical symptoms include:

  • Pain with swelling. Within 24 hours, your knee will swell. If ignored, the swelling and pain may resolve on its own. However, if you attempt to return to sports, your knee will probably be unstable and you risk causing further damage to the cushioning cartilage (meniscus) of your knee.
  • Loss of full range of motion
  • Tenderness along the joint line
  • Discomfort while walking

For a comprehensive consultation to determine the most suitable type of treatment for your ACL injuries or ACL Tearcontact us to make an appointment with our internationally renowned knee surgeon, Dr Kevin Lee at Singapore Pinnacle Orthopaedic Group.