The main symptom of chronic ACL deficiency is the knee buckling or giving out, sometimes with pain and swelling. This can happen when an ACL injury is not treated.

How is an ACL injury diagnosed?

Your doctor can tell whether you have an ACL injury by asking questions about your past health and examining your knee. The doctor may ask: How did you injure your knee? Have you had any other knee injuries? Your doctor will check for stability, movement, and tenderness in both the injured and uninjured knee.

You may need X-rays, which can show damage to the knee bones. Or you may need other imaging tests, such as an MRI. An MRI can show damage to ligaments, tendons, muscles, and knee cartilage. Arthroscopy may also be done. During arthroscopy, your doctor inserts surgical tools through one or more small cuts (incisions) in the knee to look at the inside of the knee.

How is it treated?

Start first aid right away. These first-aid tips will reduce swelling and pain. Use the RICE method. The letters stand for Rest the knee, put Ice on it, use an elastic bandage to give gentle Compression to the knee, and Elevate the leg by propping it up above the level of your heart. And at first it’s also important to move your leg as little as possible. Take over-the-counter pain medicine.

You may need to walk with crutches and use a knee immobilizer to keep your knee still for the first few days after the injury.

Your knee will need to be checked by your doctor. It's important to get treatment. If you don't, the injury may become a long-lasting problem. There are two ways to treat the injury:

• Exercises and training, also called rehab. 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.

Your treatment will depend on how much of the ACL is torn, whether other parts of the knee are injured, how active you are, your age, your overall health, and how long ago the injury occurred.

There are three main treatment goals:

• Make the knee stable if it is unsteady, or at least make it stable enough to do your daily activities.
• Make your knee strong enough to do all the activities you used to do.
• Reduce the chance that your knee will be damaged more.

How can you prevent ACL injuries?

The best way to prevent ACL injuries is to stretch and strengthen the leg muscles, especially the front and back muscles of the thigh (quadriceps and hamstrings).