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:

How ACL injury occurs

• 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.

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.

After an anterior cruciate ligament (ACL) injury, you lose leg strength and motion and stability of the knee. It is important that you regain your leg strength and motion as soon as possible, whether you choose to have surgery for your ACL injury or not. Exercises to regain muscle strength and knee motion should begin before you start treatment, whether treatment is a rehabilitation (rehab) program only or surgery plus rehab.

Key points

Schematic representation of types of ACL injuries

• After an ACL injury, your knee will not be stable, may be painful, and may have a limited range of motion. You may eventually develop osteoarthritis in the knee.
• If you do exercises to strengthen your thigh muscles (quadriceps and hamstrings) and regain knee motion soon after an ACL injury, you will be better prepared for a rehab program or for surgery with a rehab program.
• 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 through the exercises.

The exercises outlined here are common exercises used after an ACL injury. But your doctor may create a specific set of exercises for you. Check with your doctor before you do any exercises.

If you’ve recently suffered an anterior cruciate ligament injury (ACL) the following exercises can get you on the road to recovery. 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.

Exercises you can do as tolerated, include the following.

• Heel slide: Sit on the floor with legs outstretched. Slowly bend the knee of you injured leg while sliding your heel/foot across the floor toward you. Slide back into the starting position and repeat 10 times.
• Isometric Contraction of the Quadriceps: Sit on the floor with your injured leg straight and your other leg bent. Contract the quadricep of the injured knee without moving the leg. (Press down against the floor). Hold for 10 seconds. Relax. Repeat 10 times.
• Prone knee flexion: Lie on your stomach with your legs straight. Bend your knee and bring your heel toward your buttocks. Hold 5 seconds. Relax. Repeat 10 times.

Add the following exercises once knee swelling decreases and you can stand evenly on both legs without favoring the injured knee.

• Passive knee extension: Sit in a chair and place your heel on another chair of equal height. Relax your leg and allow your knee to straighten. Rest in this position 1-2 minutes several times a day to stretch out the hamstrings.
• Heel raise: While standing, place your hand on a chair/counter for balance. Raise up onto your toes and hold it for 5 seconds. Slowly lower your heel to the floor and repeat 10 times.
• Half squat: Stand holding a sturdy table with both hands. With feet shoulder’s width apart, slowly bend your knees and squat, lowering your hips into a half squat. Hold 10 seconds and then slowly return to a standing postion. Repeat 10 times.
• Knee extension: Loop one end of Theraband around a table leg and the other around the ankle of your injured leg and face the table. Bend your knee about 45 degrees agaist the resistance of the tubing and return.
• One Legged Standing: As tolerated, try to stand unassisted on the injured leg for 10 seconds. Work up to this exercise over several weeks.