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Anterior Cruciate Ligament Injury


What is an anterior cruciate ligament injury? An anterior cruciate ligament (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?

  • Car accidents and falls: Car accidents or falls may cause an ACL injury.

  • Contact sports: An ACL injury can occur when the outer or inner side of the knee gets hit hard. This often happens in contact sports, such as football, basketball, and hockey.

  • Other causes: ACL injury may also be caused by the following:

    • Forcefully twisting the knee while standing firmly in place

    • Overextending the knee

    • Suddenly stopping or changing direction while running

What are the signs and symptoms of an anterior cruciate ligament injury? You may have any of the following:

  • You may hear or feel a pop, snap, or tear when your ACL is injured.

  • You may have sudden swelling or pain in your knee.

  • You may feel your knee give way.

  • You may walk in an unusual way, such as with stiff legs.

How is an anterior cruciate ligament 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:

  • A joint x-ray is a picture of the bones and tissues in your joints. 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.

  • MRI: This scan uses powerful magnets and a computer to take pictures of your knee. An MRI is used to look for an ACL tear. You may be given dye, also called contrast, before the test. Tell healthcare providers if you are allergic to dye, iodine, or seafood. Remove all jewelry, and tell healthcare providers if you have any metal in or on your body. Metal can cause serious injury. Tell healthcare providers if you cannot lie still or are anxious or afraid of closed spaces.

  • Arthroscopy: This procedures is 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 anterior cruciate ligament injury treated? You may only need physical therapy and supportive devices if your ACL injury is mild. You may need surgery if you have an ACL tear or damage to other knee ligaments. You may need any of the following:

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

  • Medicines:

    • Pain medicine: You may be given a doctor's order for medicine to take away or decrease pain. Do not wait until the pain is severe before you take your medicine.

    • NSAIDs help decrease swelling and pain or fever. This medicine is available with or without a doctor's order. NSAIDs can cause stomach bleeding or kidney problems in certain people. If you take blood thinner medicine, always ask your healthcare provider if NSAIDs are safe for you. Always read the medicine label and follow directions.

  • Surgery:

    • Repair: An ACL tear may be repaired by reattaching the torn ligament.

    • Reconstruction: You may need reconstruction if your ACL cannot be repaired. Your ACL can be replaced with tissue taken from another part of your body, or from a donor.

  • Physical therapy: A physical therapist teaches you exercises to help improve movement and strength, and to decrease pain.

What are the risks of an anterior cruciate ligament injury?

  • Repeated injuries to your ACL can cause long-term damage. This can lead to a weak, unstable knee, even during normal activities. You may feel your knee give way more often. When the ACL is injured, other ligaments of the knee may also be affected. One or more of the menisci (cartilage shock absorbers between knee bones) may also be damaged. Injury to the ACL may cause the ligament to pull off a part of the shin bone.

  • Splints, braces, and casts can cause discomfort and limit your usual activities. If you have surgery, you could get an infection or bleed too much. Even with treatment, the knee may not be the same as it was before the injury. Without treatment, an ACL injury can cause you to have a weak knee or problems walking.

How can I manage my anterior cruciate ligament injury?

  • Rest: Rest your joint so that it can heal. Return to normal activities as directed.

  • Ice: 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.

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

  • Elevate: Keep 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 contact my healthcare provider? Contact your healthcare provider if:

  • You have a fever.

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

When should I seek immediate help? Seek help immediately or call 911 if:

  • Your toes are cold or numb.

  • Your knee becomes more weak or unstable.

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

  • Your swelling has increased or returned.

  • Your symptoms are not getting better.


You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your caregivers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

© 2014 Truven Health Analytics Inc. Information is for End User's use only and may not be sold, redistributed or otherwise used for commercial purposes. All illustrations and images included in CareNotes® are the copyrighted property of A.D.A.M., Inc. or Truven Health Analytics.

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