ACL injury

Diagnosis

During the physical exam, your doctor will check your knee for swelling and tenderness — comparing your injured knee to your uninjured knee. He or she may also move your knee into a variety of positions to assess range of motion and overall function of the joint.

Often the diagnosis can be made on the basis of the physical exam alone, but you may need tests to rule out other causes and to determine the severity of the injury. These tests may include:

• X-rays. X-rays may be needed to rule out a bone fracture. However, X-rays don't show soft tissues, such as ligaments and tendons.
• Magnetic resonance imaging (MRI). An MRI uses radio waves and a strong magnetic field to create images of both hard and soft tissues in your body. An MRI can show the extent of an ACL injury and signs of damage to other tissues in the knee, including the cartilage.
• Ultrasound. Using sound waves to visualize internal structures, ultrasound may be used to check for injuries in the ligaments, tendons and muscles of the knee.

Treatment

Treatment for ACL injury depends on how serious the injury is, your activity level and the stability of your knee. Some injuries can be treated without surgery. Others need surgery to reconstruct the ligament.

Rehabilitation

Medical treatment for an ACL injury begins with several weeks of rehabilitative therapy. A physical therapist will teach you exercises that you will perform either with continued supervision or at home. You may also wear a brace to stabilize your knee and use crutches for a while to avoid putting weight on your knee.

The goal of rehabilitation is to reduce pain and swelling, restore your knee's full range of motion, and strengthen muscles. This course of physical therapy may successfully treat an ACL injury for individuals who are relatively inactive, engage in moderate exercise and recreational activities, or play sports that put less stress on the knees.

Surgical reconstruction

If you have a complete ACL tear or are very active, you may need surgery. Your healthcare professional may recommend surgery if:

• You are an athlete and want to keep playing sports, especially those that involve jumping, cutting or pivoting.
• More than one ligament or the meniscus or cartilage in your knee also is injured.
• The injury is causing your knee to give out during everyday activities.

Before surgery, you likely will do some physical therapy to strengthen your knee and improve your range of motion.

During ACL reconstruction, the surgeon removes the damaged ligament and replaces it with a piece of tendon. This is tissue similar to a ligament that connects muscle to bone. This replacement tissue is called a graft. Your surgeon uses a piece of tendon from another part of your knee or a tendon from a deceased donor.

Physical therapy

Physical therapy after surgery is important. Successful ACL reconstruction combined with rigorous rehabilitation can usually restore stability and function to your knee. A physical therapist teaches you exercises that you can do either with the therapist's help or at home. You also may wear a brace to stabilize your knee and use crutches for a while to avoid putting weight on your knee. Rehabilitation focuses on:

• Early range of motion and pain control.
• Gradual strengthening of leg and core muscles.
• Balance and neuromuscular training to restore knee control.

There is no set time frame for athletes to return to play. Research shows that up to one-third of athletes may have another knee injury in the same or opposite knee within two years, especially with high-risk sports such as soccer. A longer recovery period may reduce the risk of reinjury.

In general, it can take a year or more before athletes can safely return to play. Your healthcare team and physical therapists test your knee's stability, strength, function and readiness to return to sports activities at various points during your rehabilitation. It is important to ensure that strength, stability and movement patterns are well-developed before you return to an activity with a risk of ACL injury.

Clinical trials

Explore Mayo Clinic studies testing new treatments, interventions and tests as a means to prevent, detect, treat or manage this condition.

Preparing for your appointment

Because ACL injury causes a lot of pain and makes the knee hard to move, many people seek medical attention right away. Others may make an appointment with their family healthcare professional. Depending on how serious your injury is, you may be referred to a healthcare professional specializing in sports medicine or an orthopedic surgeon, who specializes in bone and joint surgery.

What you can do

Before an appointment, be prepared to answer the following questions:

• When did the injury happen?
• What were you doing at the time?
• Did you hear a loud pop or feel a popping sensation?
• Was there much swelling afterward?
• Have you injured your knee before?
• Have your symptoms been constant or do they come and go?
• Do any specific movements seem to improve or worsen your symptoms?
• Does your knee ever lock or feel blocked when you are trying to move it?
• Do you ever feel that your knee is not stable or not able to support your weight?