Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Anterior Cruciate Ligament (ACL) Injuries

Font Size

Exams and Tests

An anterior cruciate ligament (ACL) injury is diagnosed through a medical history and a physical exam. A doctor who specializes in knee injuries (for example, an orthopedic surgeon or sports medicine specialist) will usually be able to accurately diagnose an ACL injury after:

  • Taking your medical history. You will be asked how you injured your knee, about your symptoms at the time of injury, whether you have had any other knee injuries, and general questions about your health.
  • Checking your knees for stability, strength, range of movement, swelling, and tenderness. Tests for stability include a Lachman test and a pivot shift test. The Lachman test compares the degree of looseness (laxity) in your knees.
  • Looking at an X-ray, which is usually done for any knee injury if there is pain, swelling, or you cannot put your weight on the leg. Although an ACL injury cannot be directly diagnosed by an X-ray, an X-ray can show whether a bone is broken, any bone fragments are in the knee, the ACL is torn from the bone (avulsion), or blood is present in the knee (effusion).

If you see your doctor soon after your injury, the pain and the degree of swelling and muscle tenseness may make it difficult for your doctor to accurately diagnose the condition.

More imaging tests

Other tests that may help your doctor see how badly the knee is injured include:

  • An MRI. It can identify an ACL tear or other problems, such as meniscus tears or other ligament injuries.
  • A CT scan. It can be done to see any small breaks in the bones.

Looking at fluid in the knee

If your knee looks red, feels warm to the touch, or is very swollen, a knee joint aspiration (arthrocentesis) may be done. This involves removing fluid from the knee joint with a needle. It is done to:

  • Help relieve pain and pressure. This may make the physical exam easier and make you more comfortable.
  • Check joint fluid for possible infection or inflammation.
  • Look for blood, which may mean there is a tear.
  • Look for drops of fat, which may mean there is a broken bone.

Local anesthetic may be injected to reduce pain and make the knee easier to examine.


WebMD Medical Reference from Healthwise

Last Updated: November 14, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
Next Article:

Hot Topics

WebMD Video: Now Playing

Click here to wach video: Dirty Truth About Hand Washing

Which sex is the worst about washing up? Why is it so important? We’ve got the dirty truth on how and when to wash your hands.

Click here to watch video: Dirty Truth About Hand Washing

Popular Slideshows & Tools on WebMD

disciplining a boy
Types, symptoms, causes.
Remember your finger
Are You Getting More Forgetful?
fruit drinks
Eat these to think better.
No gym workout
Moves to help control blood sugar.
acupuncture needle on shoulder
10 tips to look and feel good.
Close up of eye
12 reasons you're distracted.
birth control pills
Which kind is right for you?
embarrassed woman
Do you feel guilty after eating?
Epinephrine Injection using Auto-Injector Syringe
Life-threatening triggers.
woman biting a big ice cube
Habits that wreck your teeth.
pacemaker next to xray
Treatment options.
caregiver with parent
10 tips for daily life.

Women's Health Newsletter

Find out what women really need.