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Anterior Cruciate Ligament Injury, ACL Injury, ACL tear, cruciate injury

Anterior cruciate ligament injury is one of the most common ligament injuries of the knee in sport and vigorous activity. A serious injury, it can lead to functional disability and long term knee damage. However, therapeutic and surgical management is very successful.

What Is The Anterior Cruciate Ligament (ACL)?

The anterior cruciate ligament is one of the major stabilizing ligaments of the knee. Ligaments prevent unwanted movements from occurring between bones and guide the permitted movement of each joint.

The ACL consists of two strong ligament bundles, lined up in a front and rear direction inside the knee. It stops the shin bone from moving forward under the thigh bone during knee movements under the load of our bodyweight. The ACL provides 85% of the overall holding force against the shin bone moving forward inappropriately.

What Happens To Injure The Anterior Cruciate Ligament?

ACL tears are common injuries in many kinds of sport. It often occurs without any strong contact during sport, but instead as the person decelerates or makes a sudden change in direction. Often the foot is put down and then the knee twisted to one side, resulting in a pop or crack in the joint.

The ACL is a strong ligament and needs a significant force to rupture it. However, this amount of force can be produced in relatively small incidents. The most common type of ACL tear is one in the middle of the ligament, caused as the large rounded knuckle of the thigh bone pivots round during the damaging movement and cuts the ligament.

How Common Is ACL Injury?

ACL is a common injury, with one in 3000 individuals a year suffering in the United States, approximately 200,000 occurring every year. Men are most commonly injured but overall women are 2 to 8 times more likely to get an ACL tear if they are taking part in comparable sports. Reconstructing ACL’s is expensive.

What Happens When The Anterior Cruciate Ligament Is Ruptured?

A sudden popping or cracking sound is a common report during the injury which results in ACL rupture. Immediate pain is common if the rupture is complete, and because the ACL is a ligament with a good blood supply, bleeding occurs straight away.

As the knee bleeds after the injury, a haemarthrosis occurs quickly. This means the joint is full of blood. The swelling is often very tight and uncomfortable with the knee held in a fixed position of about 30 degrees bend.

If the bleeding does not immediately occur, the knee may be moderately painful until it gradually swells and the muscles go into guarding spasm. Examination of the knee is very difficult after acute injury and the knee is often examined some weeks later after the pain and inflammation have settled.

Who Gets Anterior Cruciate Ligament Injuries?

Individuals aged between 14 and 29 years are the most common sufferers of this injury, relating the most common ages of sporting activity. Female athletes have a higher incidence of ACL injuries when participating in the same sports as male athletes.

See an example of an Anterior Cruciate Ligament Reconstruction advice sheet.

See the Treatment of Acute Anterior Cruciate Ligament Injuries.


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