The ACL is one of the major bands of tissue (ligaments) connecting the thigh bone (femur) to the shin bone (tibia) at the knee joint. It can tear if you:

1.  Twist your knee while keeping your foot planted on the ground.

2.  Stop suddenly while running.

3.  Suddenly shift your weight from one leg to the other.

4.  Jump and land on an extended (straightened) knee.

5.  Stretch the knee farther than its usual range of movement.

6.  Experience a direct hit to the knee.

Anterior Cruciate Ligament (ACL) 

When you tear the ACL, you may feel a sharp, intense pain or hear a loud "pop" or snap. You might not be able to walk on the injured leg because you can’t support your weight through your knee joint. Usually, the knee will swell immediately (within minutes to a few hours), and you might feel that your knee "gives way" when you walk or put weight on it.

 

Immediately following an injury, you may be examined by a physical therapist, athletic trainer, or orthopedic surgeon.  Typical questions that are asked:

What you were doing when the injury occurred.

If you felt pain or heard a "pop" when the injury occurred.

If you experienced swelling around the knee in the first 2 to 3 hours following the injury.

If you felt your knee buckle or give out when you tried to get up from a chair, walk up or down stairs, or change direction while walking.

The medical professional may perform gentle "hands-on" tests to determine the likelihood that you have an ACL tear, and may use additional tests to assess possible damage to other parts of your knee.

An orthopedic surgeon may order further tests, including magnetic resonance imaging (MRI), to confirm the diagnosis and rule out other possible damage to the knee.

Most people who sustain an ACL tear will undergo surgery to repair the tear; however, some people may avoid surgery by modifying their physical activity to relieve stress on the knee. A select group can actually return to vigorous physical activity following rehabilitation without having surgery.

Your surgeon can help you determine if nonoperative treatment (rehabilitation without surgery) is a reasonable option for you. If you elect to have surgery, your surgeon will help you prepare for surgery and your physical therapist will help you recover your strength and movement following surgery.