ACL (Anterior Cruciate Ligament) Tears

Overview

What is an ACL tear? What does it feel like?

An ACL tear is damage to the anterior cruciate ligament (ACL), located at the center of your knee. The tear may be partial (the ligament is torn a little) or total (the ligament is torn into two pieces). It will hurt if you tear your ACL. Your knee may “give out” (collapse or buckle) and you may hear or feel a pop. Typically, your knee will immediately start to swell up.

“Ligament” is what the medicine world calls the tough bands of tissue that connect bones or hold organs in place. The word “anterior” means “towards the front of the body.” Cruciate means “cross-shaped,” and in medical terms it refers to the two ligaments in your knee that form the shape of a cross: the ACL in the front and the posterior cruciate ligament (PCL) in the back.

What is the anterior cruciate ligament (ACL)?

Your knees are made up of bones, ligaments, tendons and cartilage. The anterior cruciate ligament (ACL), which is located in the front center of your knee, connects the thigh bone (femur) to the shin bone (tibia). It is one of four primary ligaments located in your knee:

  • Anterior cruciate ligament (ACL).
  • Medial collateral ligament (MCL).
  • Lateral collateral ligament (LCL).
  • Posterior cruciate ligament (PCL).

The main function of the ACL is to stop forward movement and rotation of the shin bone on the thigh bone.

What are the types of ACL tears?

When you hurt a ligament, your healthcare provider may grade the injury on a one to three scale, with three being the most severe:

  • Grade One: Your ligament has been stretched, but it still does its job of stabilizing the knee joint.
  • Grade Two: Your ligament has been stretched and loosened. It’s partially torn. (This grade is rare.)
  • Grade Three: Your ligament is torn – divided into two pieces. This is a very severe injury.

ACL tears are often accompanied by injuries to the collateral ligaments, joint capsule, articular cartilage or the menisci (cartilage pads).

How common are ACL tears? Who is at risk?

ACL tears are a very common knee injury. In the United States there are between 100,000 and 200,000 incidents every year. They’re common in athletes, especially those who do start-stop, sudden change in direction sports like football, basketball, soccer and volleyball. You’re also at a higher risk if you work a strenuous job that requires climbing, pivoting or jumping.

An ACL tear can happen to anyone at any age, but females are four times more likely to have an ACL tear than males. Experts have yet to agree on why females are more prone. Some think this is because of different physical conditioning, neuromuscular control, or muscle strength. Others think that it’s because of a difference in pelvis and lower leg alignment, looser ligaments, or how estrogen affects a woman’s ligaments. Differences in how women jump and land could also be a factor.

Can you walk with a torn ACL?

Some people feel stable enough to walk, as long as they do it slowly and carefully. Others choose to use crutches in case their knee “gives out” (collapses or buckles).

Do ACL tears hurt?

Yes. You will feel pain and may hear or feel a pop when the injury happens.

What happens if a child tears their ACL?

Children and adolescents are still growing. Reconstructing an ACL risks growth plate injury, and that can lead to bone growth problems. Sometimes the surgeon won’t operate on the ACL until the child is older and their bones are mature, of they’ll use special techniques to avoid damage to the growth plate.

Symptoms and Causes

What causes ACL tears?

Most ACL tears are non-contact injuries. This means that they are not caused by, for example, another player kicking your knee. They can occur in several different ways, including when you:

  • Suddenly stop running.
  • Slow down when you’re running.
  • Land awkwardly from a jump.
  • Change direction suddenly, twisting your knee.
  • Collide with someone else, like during a football tackle.

Sometimes – about half the time – other damage happens along with ACL tears. There may be damage to other parts of the knee such as the other ligaments and/or the cartilage (a gel-like connective tissue). 70 % of people with ACL tears will have injury to one or both of the menisci (the cushions in the knee that help to protect the cartilage).

What are the signs and symptoms of an ACL tear?

When your ACL tears, you might feel or hear a pop in your knee, or feel like your knee has “given out.” Other symptoms include:

  • Pain.
  • Swelling that starts immediately (but can start four to six hours after the injury) and lasts for two to four weeks.
  • Loss of range of motion in your knee.
  • Tenderness.
  • Discomfort when you walk.

Diagnosis and Tests

How is an ACL injury diagnosed? What tests are done?

Part of the diagnosis process is ruling out other possible reasons for your knee pain. Your healthcare provider might order an x-ray to make sure no bones are broken. He or she will take a medical history and ask specific questions about the knee pain. They will examine the injured knee and compare it to your other knee. This examination is very accurate at detecting ACL tears.

An MRI will probably be ordered. MRIs show the ligaments, and a torn ACL will show up clearly. This might not be necessary, however, because the comparison between knees may reveal that the ligament is torn.

What questions might my healthcare provider ask to diagnose an ACL tear?

  • How did you injure your knee?
  • When did the injury happen?
  • When did the swelling start?
  • What part of your knee hurts?
  • Did you hear a sound when the injury happened?
  • Have you torn your ACL before?

Management and Treatment

What is the treatment for an ACL injury?

Do R.I.C.E. therapy immediately after the injury:

  • R: Rest.
  • I: Ice.
  • C: Compression.
  • E: Elevation.

The type of treatment you receive is up to you. Many people with ACL tears decide to have surgery so that they can return to the activities they did before the injury. If your activity level isn’t as high, you might choose to not have surgery. But, keep in mind that your torn ACL won’t heal on its own.

What are the surgical treatments? How is the surgery done?

Surgery to reconstruct a torn ACL is done with a graft of a tendon (tendons connect muscles to bones) from your body, such as a hamstring (from the back of the thigh), or the kneecap/patellar tendon (from the front of the knee). Occasionally, a cadaver tendon (a tendon from someone who died and donated his/her body to science) can be used in older individuals who are still very active. Cadaver tendons are typically not used in young athletes because of the higher rates of re-tear.

The surgery is minimally invasive, which means that instead of making a large incision with a scalpel, the surgeon uses an arthroscope, a thin wand-like instrument. The surgeon inserts the arthroscope and the working instruments through small incisions in your knee.

What happens after ACL surgery?

After surgery you’ll need to keep your wound clean and dry. You’ll use ice to reduce swelling and pain. You may use a brace and crutches.

You’ll have physical therapy to strengthen your knee and the muscles around it. The first few days following surgery, you’ll perform gentle range-of-motion and simple strengthening exercises, and some weight-bearing exercises. Physical therapy will start within the first week, including advanced strengthening and balance activities.

After about 12 to 16 weeks, if you’re not an athlete, sport-specific activities are added to the rehabilitation program, such as hopping, jumping and agility drills. An athlete should be able to return to normal activity about six to nine months after the ACL surgery.

How soon after treatment will I feel better? What’s the recovery time?

Six to nine months is typically how long it takes to recover from ACL surgery.

What are the nonsurgical treatments?

Nonsurgical treatments include bracing and physical therapy:

  • Bracing: Putting a brace around your knee will keep it stable. You’ll have to use crutches so that you don’t put weight on that leg.
  • Physical therapy: Exercises will help your knee function and strengthen the leg muscles around it, supporting it.

Keep in mind that if you choose not to have surgery, you’re at a higher risk of re-injuring your knee.

What are the complications of surgery?

  • Infection. Infection is rare, but still a risk with any type of surgery.
  • Stiffness. Stiffness in the knee is common post-surgery, but physical therapy can help it. This can be avoided by performing rehabilitation to regain all of your motion before surgery.
  • Viral transmission. Receiving a graft from a cadaver always comes with a risk of contracting diseases like HIV and Hepatitis C. There is less than a one in a million chance that you’ll get an HIV-infected graft.
  • Blood clot. A blood clot can be life-threatening, but it’s rare. The clot can break off in the bloodstream and cause a pulmonary embolism in the lungs or a stroke in the brain.
  • Kneecap pain. This complication is common when using patellar tendon grafts.
  • Growth plate injury. Early ACL reconstruction in a child or adolescent risks this. If possible, the surgeon will delay the procedure until the skeleton is fully grown or utilize special techniques to avoid injuring the growth plate.

Prevention

Can ACL injuries be prevented?

If you’re an athlete then it may not be possible to completely eliminate ACL injuries, but various training techniques can minimize the risk of tearing the ACL.

If you play soccer, basketball and volleyball, you should be especially mindful of two things: how you take hard, quick steps to accelerate in another direction (or “cut”) and how you land on your feet from a jump or a step (“plant”).

These cutting and planting maneuvers cause about 70% of all ACL injuries.

The jumping, landing and pivoting involved in these sports all stress the knee’s ACL – particularly in female athletes. Initiating a cut (or landing after a jump) can compromise the ACL’s ability to resist rotational forces. Planting incorrectly can overwhelm the ACL’s ability to move the knee the way it is designed to do.

Why are women at higher risk for ACL injuries?

Male and female athletes tend to have differences in how they maneuver in a jump or cut, which puts women at higher risk for injury.

Women tend to activate their quadriceps first, while men tend to activate their hamstrings first. This difference in activation may alter the amount of strain applied to the ACL and other knee ligaments.

In addition, after a jump, women tend to land with their knees closer together than men. Athletes who land with their knees farther apart seem to have less risk of ACL injury.

Fatigue as factor in ACL injuries

Fatigue is a hazard for both male and female athletes. Tired athletes are more likely to use poor mechanics. For example, they may land with their knees closer together. This is especially true when a fatigued athlete makes a split-second decision to execute an unexpected move.

Proper training can help prevent injuries

Studies show that training programs supervised by sports health professionals improve athletes’ leg strength and jump-landing techniques.

Proper training decreases ACL injury rates in basketball, volleyball and soccer. The techniques that improve ACL safety can also enhance performance, and increase vertical jump height, acceleration and the ability to change direction.

Nothing can prevent ACL injuries altogether. But exploring their potential causes and maximizing prevention strategies can stop the “pop” and its frustrating consequences.

Outlook / Prognosis

Can ACL tears be cured?

With time, surgery and physical therapy, you should regain full use of your knee within six to nine months.

Will an ACL tear ever happen again?

You can re-tear your ACL, yes. The risk or re-tear is generally considered to be five to seven percent.

Living With

Can I live a normal life with an ACL tear?

Yes, but it may take some time before you’re completely back to how you were before the injury. Whether you choose to have surgery or not, with physical therapy you will eventually be back to normal and able to live your life.

Is an ACL tear “career-ending” for athletes?

After surgery it takes about six to nine months of physical therapy before an athlete is ready to return. By then he or she will no longer have swelling or pain. The full range of motion should be restored and all of the balance, strength and endurance should be back. Most athletes will return to their prior level of functioning.

How do I take care of myself?

Follow your healthcare provider’s instructions, including those of your physical therapist. Work hard at your physical therapy. Take medications as prescribed.

When should I see my healthcare provider?

See your healthcare provider immediately when you injure your knee. They’ll need to evaluate the injury, reduce the swelling, give you pain medication and determine the next steps.

What questions should I ask my healthcare provider?

  • What are the pros and cons for surgery to repair my ACL tear?
  • Do I have a partial ACL tear or is it torn in two?
  • What medications should I take?
  • Do I need to see a specialist?
  • Who is a good orthopedic surgeon?
  • Should I see a specialist in sports medicine?
  • When can I return to work/school?
  • How soon can I have surgery?
  • How long do you predict it will take me to recover?
  • What kind of graft is best for me?

A note from Cleveland Clinic

An ACL tear will only temporarily stop you from working your job or playing the sports you love. Remember, your healing depends on your own choices: choices to use crutches, to have surgery or not, to work hard at your physical therapy, etc. If you commit to your physical therapy and listen to your healthcare providers’ instructions, then your life will be back to “normal” soon.

Last reviewed by a Cleveland Clinic medical professional on 10/19/2020.

References

  • American Academy of Orthopedic Surgeons. . Accessed 10/18/2020.Anterior Cruciate Ligament (ACL) Injuries (http://orthoinfo.aaos.org/topic.cfm?topic=a00549)
  • American Academy of Orthopedic Surgeons. Accessed 10/18/2020.ACL Injury: Does It Require Surgery? (http://orthoinfo.aaos.org/topic.cfm?topic=a00297)
  • Cimino F, Volk BS, Setter D. Anterior Cruciate Ligament Injury: Diagnosis, Management, and Prevention. Am Fam Physician. 2010 Oct 15;82(8):917-922. Accessed 101/8/2020.
  • American Academy of Pediatrics. . Accessed 10/18/2020.Anterior Cruciate Ligament Injuries: Diagnosis, Treatment, and Prevention (http://pediatrics.aappublications.org/content/133/5/e1437)
  • Merck Manual. . Accessed 10/18/2020. Knee Sprains and Related Injuries (https://www.merckmanuals.com/home/injuries-and-poisoning/sprains-and-other-soft-tissue-injuries/knee-sprains-and-related-injuries)
  • Merriam-Webster. . Accessed 10/18/2020. Ligament (https://www.merriam-webster.com/dictionary/ligament#:~:text=Medical%20Definition%20of%20ligament,and%20flexible%2C%20but%20not%20extensible)
  • Radiopaedia. . Accessed 101/8/2020. Anterior Cruciate Ligament Tear (https://radiopaedia.org/articles/anterior-cruciate-ligament-tear?lang=us)
  • Evans J, Nielson JI. Angerior Cruciate Ligament (ACL) Knee Injuries. 1st ed. Treasure Island (FL): StatPearls Publishing; 2020. Accessed 10/18/2020.
  • Cimino F, Volk, BS, Setter D. Anterior Cruciate Ligament Injury: Diagnosis, Management, and Prevention. Am Family Physician: 2010;82(8):917-922. Accessed 10/18/2020.

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