The anterior cruciate ligament (ACL)


Your ACL, anterior cruciate ligament, is the ligament that lies in the middle of the knee joint on the front portion. This ligament connects your thigh and lower leg bones together along with the other ligaments in your knee that each help keep the knee joint stable. Injury to your ACL is unfortunately common in athletes, especially in sports requiring significant amounts of running or contact. Many surgeons recommend waiting to perform surgery until after swelling and range of motion have returned to the knee. This phase is often called pre-habilitation, which involves physical therapy to prepare for surgery.

Cardiovascular Exercise

If only the ACL is injured, stability in the knee will be affected but you can still perform cardiovascular exercises. This will improve circulation to the knee and improve range of motion prior to surgery. Recommended exercises include walking, riding a stationary bicycle and swimming, although you may wish to avoid the breaststroke, which can be too hard on your knee. Avoid contact sports and running.

Strengthening Exercises

Strengthening exercises for the knee do not have to involve a wide range of motion. Until your range of motion returns following ACL injury, you may perform isometric exercises. One example is lying on your back and placing a rolled-up towel underneath your feet. Keep your legs straight, as you press the knee toward the floor, tensing your quadriceps muscles in the front of the thighs. Another strengthening exercise involves lying on a table on your stomach, with your lower legs hanging off the table. Keep your legs straight as you lift them up — first straight, then bending your legs toward your buttocks.

Range of Motion Exercises

Prior to surgery, your physical therapist will likely set a goal for you to fully extend your leg. To accomplish this, you will use exercises like towel extensions, where you wrap a towel around the foot of the affected leg, holding an end in each hand. Pulling the towel toward you can help stretch the knee. Another exercise known as wall slides involves lying on your back and placing your feet flat on a wall, walking one foot and then the other up the wall.


Rehabilitation exercises prior to ACL tear repair surgery help prevent the development of scar tissue following surgery. Because the muscles and tendons have more time to heal during the pre-rehabilitation period, you are less likely to experience scarring that affects your range of motion. Increasing strength also enhances stability after surgery, speeding your recovery period.