The anterior cruciate ligament (ACL) is one of four knee ligaments that connect the upper leg bone (femur) with the large lower leg bone (tibia). The ACL stabilizes knee movement by:

• Preventing the knee from sliding or twisting abnormally when the leg is straight or slightly bent.
• Preventing the knee from being stretched or straightened beyond its normal limits (hyperextended).
• Supporting the knee ligaments that keep the knee from bending sideways.

See a picture of the knee and the ACL.

When the ACL tears, the blood vessels around the ligament tear and blood can fill the knee joint, causing swelling. This can result in both pain and loss of motion. The inactivity following an ACL injury often results in weakening of the muscle in the front of your thigh, the quadriceps. If nothing is done after an ACL injury, you may develop chronic ACL deficiency—your knee may become less stable, leading to abnormal knee joint movement and premature osteoarthritis.

Treatment is needed for an ACL injury. Treatment is either a rehab program or ACL surgery followed by a rehab program. Surgery is generally more successful if you condition your knee and surrounding muscles before starting your treatment. This can be achieved by doing a few simple exercises. Your doctor will help you decide when to start these exercises.

It is important to begin doing some simple exercises after injuring your ACL and before treatment begins. Regaining leg strength and knee motion will help your treatment be more successful, whether your rehab program is done in conjunction with surgery or not.

Quad sets, straight-leg raises, and heel slides are common exercises used after an ACL injury. As symptoms decrease and you are able to bear weight, side-lying leg lifts, glute sets, bridges, mini-squats against a wall, heel raises, and prone hamstring curls might be added. But your doctor may want you to tailor exercises to your specific injury. Check with your doctor before you do any exercises.

You should start slowly and gradually increase the intensity of the exercises. Do not push yourself to the point that you feel pain. Talk to your doctor about how to best progress.

• Bridging
• Glute Sets
• Hamstring Curls
• Heel Raises
• Heel Slides
• Quad Sets
• Shallow Standing Knee Bends
• Straight-Leg Raise to the Front
• Straight-Leg Raise to the Outside

For more information about exercises for an ACL injury, talk to:

• Your doctor.
• A sports medicine specialist.
• A physical therapist.