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Anterior Cruciate Ligament Injury

What is an anterior cruciate ligament (ACL) injury?

An ACL injury is a partial or complete tear of the ACL. The ACL is a ligament in your knee that connects the tibia (shin bone) to the femur (thigh bone). Ligaments are strong tissues that connect bones together. The ACL stops the tibia from sliding too far forward and keeps the knee stable.

What causes an anterior cruciate ligament injury?

Trauma such as from a car accident or a fall may cause a tear in the ACL. An ACL injury may happen when the outer or inner side of the knee gets hit hard. This often happens in contact sports, such as football, basketball, and hockey. You may also injure your ACL by twisting your knee while you are standing, overextending your knee, or suddenly stopping or changing direction while you are running.

What are the signs and symptoms of an ACL injury?

  • A pop, snap, or tear when your ACL is injured

  • Sudden swelling or pain in your knee

  • The knee gives way

  • A change in the way you walk, such as with stiff legs

How is an ACL injury diagnosed?

Healthcare providers may test the function of your ACL by moving your knee, leg, or foot in different directions. You may be asked to lean or hop using your leg with the injured knee. Tell your healthcare provider if you feel pain while you do these or other activities. Both of your knees may be checked for any abnormal movement. You may need the following tests:

  • An x-ray or MRI may be used to look for an ACL tear. You may be given contrast liquid to help the pictures show up better. Tell a healthcare provider if you have ever had an allergic reaction to contrast liquid. Do not enter the MRI room with anything metal. Metal can cause serious injury. Tell the healthcare provider if you have any metal in or on your body.

  • Arthroscopy is a procedure used to look inside your knee for an ACL injury. A small incision is made in your knee and a scope is inserted. The scope is a long, bendable tube with a camera and light on the end.

How is an ACL injury treated?

  • Support devices such as a knee brace may be used to limit your movement and protect your knee. You may need to use crutches to help decrease your pain as you move around.




  • Surgery may be needed if you have an ACL tear or damage to other knee ligaments.

How can I manage my anterior cruciate ligament injury?


  • Ice helps decrease swelling and pain. Ice may also help prevent tissue damage. Use an ice pack, or put crushed ice in a plastic bag. Cover the ice pack with a towel and place it on your injured ligament for 15 to 20 minutes every hour. Use the ice for as long as directed.

  • Compression provides support and helps decrease swelling and movement so your joint can heal. Ask your healthcare provider if you should wrap an elastic bandage around your injured ligament.

  • Elevate your injured area raised above the level of your heart as often as you can. This will help decrease or limit swelling. Elevate the injured area by resting it on pillows.

When should I seek immediate care?

  • Your toes are cold or numb.

  • Your knee becomes more weak or unstable.

  • Your pain has increased or returned, even after you take your pain medicine.

  • Your swelling has increased or returned.

  • Your symptoms are not getting better.

When should I contact my healthcare provider?

  • You have a fever.

  • You have questions or concerns about your condition or care.

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