Patient education: Anterior cruciate ligament tear (The Basics)

What is an anterior cruciate ligament tear? — An anterior cruciate ligament tear is a type of knee injury. This injury usually causes swelling and pain in the knee. It also makes the knee feel unstable, or like it is "giving out."

A ligament is a tough band of tissue that connects 1 bone to another. The anterior cruciate ligament, also called the "ACL," connects the thigh bone (called the "femur") to the shin bone (called the "tibia") (figure 1). It works with another ligament to keep the knee from moving too far forward or backward.

What are the symptoms of an ACL tear? — When people have an ACL tear, they often say they heard a "pop" when the injury happened. This injury tends to happen when people are playing sports that involve quick changes in direction, such as basketball or soccer. It can also happen when a person slows down suddenly while changing direction or lands from a jump.

Within a few hours of an ACL injury, the knee usually swells. It can also feel unstable or wobbly, like it can't hold your weight.

Is there a test to check for an ACL tear? — Yes. If your doctor or nurse thinks you might have an ACL tear, they will do an exam. They might also order an imaging test called an MRI. This test creates a picture of the inside of your knee. But an MRI is not always needed.

Is there anything I can do on my own to feel better? — Yes. Some people feel better if they do certain exercises. Ask your doctor or nurse which exercises might help you feel better.

Should I see a doctor or nurse? — See your doctor or nurse if you have the symptoms described above or if you think you might have an ACL injury.

How are ACL tears treated? — Everyone with an ACL tear has to do special exercises for a while after their injury. These exercises are called "rehabilitation," or "rehab." They help you strengthen your knee and get back the ability to move it around.

After their swelling and pain get better, some people have surgery to rebuild the torn ACL. For this surgery, doctors remove the damaged ACL. Then, they replace it with a strip of tissue taken from another part of the leg. (Sometimes, the tissue comes from another person's leg.) After surgery, people do a lot more rehab to make sure the rebuilt ACL works well.

But surgery is not always needed. Some people with a torn ACL do not have surgery and instead just do more rehab work.

The decision about whether to have surgery depends on a lot of things, including:

●How unstable your knee feels after doing some rehab

●How severe your injury is – Surgery is often needed if other parts of the knee are also injured.

●What kind of physical activity you do – If you are very active or do a lot of things that involve twisting or turning your knee, surgery might be a good idea.

●Your age

●If you have other health problems

●If you are willing to do a lot of rehab after surgery to make sure the repaired ACL works well

How do I decide whether to have surgery? — You and your doctor will work together to decide if surgery is right for you. As you talk about surgery, ask:

●How will my rehab be different if I have surgery or do not have surgery?

●What are the risks of surgery?

●What are the risks of not having surgery?

●How well will my knee work if I have surgery?

●Will I be able to keep doing my favorite physical activities if I do not have the surgery?

Can ACL injuries be prevented? — You can reduce your chances of getting an ACL injury if you:

●Stay active and do exercises that make the muscles that support the knee strong and flexible. As part of your training, work on your balance. For example, practice standing on 1 foot.

●Learn how to move so there is less stress on the knee during sports. This might involve talking to a fitness expert. They can show you how to move and position your body to protect your knee, especially during physical activity.

More on this topic

Patient education: Knee sprain (The Basics)
Patient education: Knee arthroscopy (The Basics)

Patient education: Anterior cruciate ligament injury (Beyond the Basics)