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ACL Injury

Medically reviewed by Last updated on Jun 6, 2022.

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. The ACL stops the tibia from sliding too far forward and keeps the knee stable.

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
  • Trouble putting weight on your leg or straightening the knee

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 knee show up better in pictures. 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?

  • NSAIDs , such as ibuprofen, help decrease swelling, pain, and 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.
  • Acetaminophen decreases pain and fever. It is available without a doctor's order. Ask how much to take and how often to take it. Follow directions. Read the labels of all other medicines you are using to see if they also contain acetaminophen, or ask your doctor or pharmacist. Acetaminophen can cause liver damage if not taken correctly.
  • Prescription pain medicine may be given. Ask your healthcare provider how to take this medicine safely. Some prescription pain medicines contain acetaminophen. Do not take other medicines that contain acetaminophen without talking to your healthcare provider. Too much acetaminophen may cause liver damage. Prescription pain medicine may cause constipation. Ask your healthcare provider how to prevent or treat constipation.
  • Surgery may be needed if you have an ACL tear or damage to other knee ligaments.

Treatment options

The following list of medications are in some way related to or used in the treatment of this condition.

View more treatment options

How can I manage my ACL injury?

  • Rest your leg as directed. Your healthcare provider will tell you when you can return to your normal daily activities. You may not be able to play certain sports until your knee heals. Talk to your provider about sports you currently play. You may need to make a safe plan to start playing the sport again.
  • Apply ice to decrease swelling and pain. Use an ice pack, or put crushed ice in a plastic bag. Cover the bag with a towel and place it on the area for 15 to 20 minutes every hour. Use the ice for as long as directed.
  • Apply compression to support the ligament and help decrease swelling. Your healthcare provider can tell you how often to do this.
    How to Wrap an Elastic Bandage
  • Elevate the area above the level of your heart as often as you can. This will help decrease or limit swelling. Rest your lower leg and foot on pillows. Do not put the pillow directly under your knee.
    Elevate Leg
  • Use support devices as directed. A knee brace may be used to limit movement and protect your knee. You may need to use crutches to help decrease pain as you move around.
    Hinged Knee Braces
  • Go to physical therapy as directed. A physical therapist can teach you exercises to help improve movement and strength, and to decrease pain. The exercises can also help increase the range of motion in your knee.

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 call my doctor?

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

Care Agreement

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 healthcare providers 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.

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.