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Anterior Cruciate Ligament (ACL) Injury

The anterior cruciate ligament (ACL) is one of the four ligaments that join the thighbone (femur) to the shinbone (tibia). The ACL helps keep the knee stable. You can tear it when you plant your foot and then push off, change direction, or twist. This can happen during sports like soccer or basketball. Your ACL can also tear when you get hit around your knee. This is more common in a sport like football.

Treatment usually starts with staying off the leg and elevating it, icing the knee, and using a compression bandage.

Your doctor may discuss letting your knee heal with time and physical therapy (PT). You may choose surgery to repair your ACL, especially if you're very active, if other parts of your knee are injured, or if your knee is unstable. Whether you have surgery or not, PT to help you strengthen the muscles around your knee is important.

What are the symptoms of an anterior cruciate ligament (ACL) injury?

Symptoms of a severe and sudden (acute) ACL injury include:

  • Feeling or hearing a pop in the knee at the time of injury.
  • Pain on the outside and back of the knee.
  • The knee swelling within the first few hours of the injury. This may be a sign of bleeding inside the knee joint. Swelling that occurs suddenly is usually a sign of a serious knee injury.
  • Limited knee movement because of pain or swelling or both.
  • The knee feeling unstable, buckling, or giving out.

After an acute injury, you will probably have to stop whatever you are doing because of the pain. But you may be able to walk.

How can you help prevent anterior cruciate ligament (ACL) injuries?

One way to help prevent ACL injuries is to stretch and strengthen the muscles in the legs and body. There are also training programs that teach movements that may prevent injury and help with balance. Warming up before training or competing may also help. Some ACL injuries can happen anyway.

What causes an anterior cruciate ligament (ACL) injury?

You can tear your ACL when you plant your foot and then push off, change direction, or pivot. This can happen during certain sports, like soccer or basketball.

You can also tear it from getting hit in your leg or knee during a contact sport like football or in high-speed sports like skiing.

Injuries like those from a car crash, stepping in a hole, or jumping or falling from a height can also cause an ACL tear.

How is an anterior cruciate ligament (ACL) injury diagnosed?

To diagnose an ACL injury, your doctor will ask you to describe how you injured your knee and what you felt. The doctor will check your knee for swelling or tenderness. They may gently push and pull on your leg to see if the knee joint moves in an abnormal way. The exam is usually done on both legs so the doctor can compare one leg to the other to see what's normal for you.

You may have an X-ray to help make sure there isn't a different injury, like a broken bone. Ligaments can't be seen on an X-ray. An MRI is an imaging test that can help show the ACL. It can help your doctor see if you have an ACL tear. Often an injury that causes an ACL tear also injures other ligaments or the cartilage called the meniscus. An MRI can help your doctor diagnose these other injuries.

How is an anterior cruciate ligament (ACL) injury treated?

Treatment for an ACL injury includes:

  • First aid right away. This is to help take care of symptoms like pain and swelling.
    • Put ice or a cold pack on your knee for 10 to 20 minutes several times a day. Put a thin cloth between the ice and your skin.
    • Elevate your injured knee when possible.
    • Use crutches and a knee immobilizer.
    • Take over-the-counter pain medicine, such as acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs). Be safe with medicines. Read and follow all instructions on the label.
  • Nonsurgical treatment. This is also called rehab. It can include controlling swelling, increasing knee mobility, strengthening the muscles, and working on balance. If you're returning to a sport or intense activity, you may also work on techniques to reduce the risk of injury. It takes several months of rehab for your knee to get better.
  • Surgery. You and your doctor can decide if rehab is enough or if surgery is right for you. If you have surgery, you will also have several months of rehab afterward.

You don't have to decide about surgery right away. Usually, your doctor would not do surgery for at least several weeks after your injury. This allows time for the swelling in your knee to go down. It also gives you time to strengthen the muscles around the knee and make sure you can move your knee well.

How is surgery used to treat anterior cruciate ligament (ACL) injuries?

Surgery for an ACL tear can help you stabilize your knee and return to activity. Surgery may include:

  • Reconstruction surgery. The surgeon replaces the ACL with tissue called a graft. Usually an autograft is used. For an autograft, the surgeon uses tendon tissue from your own body. This can be done safely. For an allograft, the tendon tissue is from a deceased donor.
  • When the damaged ACL pulls a piece of bone off, it is called an avulsion fracture. The surgeon may reconnect the bone fragment to the area it was pulled from.
Physical rehabilitation for anterior cruciate ligament (ACL) injuries

Rehabilitation (rehab) is needed after most ACL injuries, with or without surgery. It'll help you regain normal range of motion and flexibility in your knee. Rehab programs also strengthen the knee and the muscles around it, leading to better knee stability.

Your doctor or physical therapist will design a rehab program for you that considers your normal level of activity, your physical fitness, and the extent of your injury.

A rehab program should include exercises for:

  • Flexibility.
  • Strength.
  • Endurance.
  • Coordination and agility training.

How quickly you recover from your ACL injury depends on how severe the injury was, how extensive any surgery was, and how consistent you are to follow the program. The rehab program usually lasts from several months to a year.