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What are the Different Causes of ACL Injuries?

Christina Edwards
Christina Edwards

The anterior cruciate ligament, or ACL, works together with the posterior cruciate ligament, or PCL, to stabilize the knee and keep the lower part of the leg from going too far forward. ACL injuries are frequent injuries reported by athletes, and they are often caused by a hard hit to the knee, rotating the knee, or extending the knee beyond its natural state. Depending on the severity of the an ACL injury, treatment can include physical therapy or surgery.

An ACL tear or injury sometimes occurs after a hard hit to the knee, especially the front or exterior side of it. This causes the ligament to stretch, and possibly cause a tear. ACL injuries of this sort are typically more common in certain sports, such as tackle football or rugby.

Rugby players are prone to ACL injuries.
Rugby players are prone to ACL injuries.

ACL injuries can also be caused by rotating the knee too much. Common examples of his type of ACL injury include when an athlete either slows or stops, then suddenly changes direction. Football, tennis, and soccer all can cause ACL injuries when athletes rotate their knees. These injuries typically are caused by athletes making sudden stops and twists.

A diagram of the knee, showing the anterior cruciate ligament (ACL).
A diagram of the knee, showing the anterior cruciate ligament (ACL).

Knee hyperextension occurs when a person straightens or extends the knee joint beyond its normal range of motion. Doing this can often result in ACL injuries, and it should be avoided. Landing from a jump wrong, with the knee straight, for example, can result in hyperextension of the knee. Sports in which these injuries often occur include basketball, skiing, and gymnastics.

Football players have a high risk of ACL injuries.
Football players have a high risk of ACL injuries.

Although most ACL injuries typically occur to athletes while playing their chosen sports, just about anyone can suffer from an ACL injury. For example, these injuries can occur during just about any type of accident, including a car accident or a nasty fall. Also, recurring trauma to the knee can result in small rips or tears to the ACL, or any other ligament in the knee. These small tears can eventually get larger if a person is not careful and, eventually, result in a more serious ACL tear.

A medical professional wrapping a person's knee with an elastic bandage for support.
A medical professional wrapping a person's knee with an elastic bandage for support.

The most commonly reported signs of ACL injuries include a loud pop and intense pain when the injury occurs. After the injury, the affected knee often swells severely. Because this is a main ligament in the knee that helps people balance when standing or walking, some unsteadiness is almost always reported. People with ACL injuries often feel as though their injured knee will suddenly give out on them, and they may need to use crutches or a cane to help support them when they walk.

A man wearing a brace for knee hyperextension.
A man wearing a brace for knee hyperextension.

Physicians generally recommend the RICE treatment for ACL injuries. RICE stands for rest, ice, compression, and elevation. Immediately following the injury, the affected knee should be rested. To reduce the swelling, ice should be applied every few hours, an ACE™ bandage should be wrapped around it, and it should be elevated. Over the counter pain medication can be taken to help relieve the pain.

Knee injuries are common in sports.
Knee injuries are common in sports.

In more serious cases, physical therapy, or even surgery may be required. During surgery, a ligament is often taken from a different area of the leg, or possibly another donor. Knee surgery to repair a torn ACL is often quite successful, and many people are able to continue almost all physical activity within six months.

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    • Rugby players are prone to ACL injuries.
      Rugby players are prone to ACL injuries.
    • A diagram of the knee, showing the anterior cruciate ligament (ACL).
      By: Alila
      A diagram of the knee, showing the anterior cruciate ligament (ACL).
    • Football players have a high risk of ACL injuries.
      By: Pete Saloutos
      Football players have a high risk of ACL injuries.
    • A medical professional wrapping a person's knee with an elastic bandage for support.
      By: Gennadiy Poznyakov
      A medical professional wrapping a person's knee with an elastic bandage for support.
    • A man wearing a brace for knee hyperextension.
      By: Julián Rovagnati
      A man wearing a brace for knee hyperextension.
    • Knee injuries are common in sports.
      By: Stephen Coburn
      Knee injuries are common in sports.
    • A torn ACL typically requires surgery.
      By: derege
      A torn ACL typically requires surgery.
    • Damage to the anterior cruciate ligament (ACL) can occur when the knee rotates too much.
      By: Martinan
      Damage to the anterior cruciate ligament (ACL) can occur when the knee rotates too much.
    • Soccer players can suffer ACL injuries when they make sudden stops or twists.
      By: Paco Ayala
      Soccer players can suffer ACL injuries when they make sudden stops or twists.
    • The ACL is the most commonly injured ligament in the knee.
      By: Dirima
      The ACL is the most commonly injured ligament in the knee.
    • The goal of sports medicine is to prevent injuries and optimize a healthy lifestyle.
      By: Monkey Business
      The goal of sports medicine is to prevent injuries and optimize a healthy lifestyle.
    • Ice should be applied as soon as a knee injury occurs.
      By: Rido
      Ice should be applied as soon as a knee injury occurs.