The Anterior Cruciate Ligament (ACL) is one of the most commonly injured ligaments in the knee. Ligaments are strong non-elastic fibers that connect bones. The ACL crosses inside of the knee, connecting the thighbone to the leg and provides stability to the knee joint.
The knee is composed of three bones. The femur, or thighbone, sits on top of the tibia, the larger leg bone. The patella, or kneecap, glides in a groove on the end of the femur. The anterior cruciate ligament and the posterior cruciate ligament cross inside of the knee joint. These two ligaments help to keep the joint aligned. They counteract excessive forward and backward forces and prohibit displacement of the bones. They also produce and control rotation of the tibia.
The ACL can tear during strong twisting motions of the knee. The ACL can also tear if the knee is hyperextended or bent backwards. People frequently tear the ACL while pivoting, landing awkwardly from a jump, changing directions suddenly, or abruptly slowing down from running. ACL tears occur most frequently in young athletes. Football, basketball, skiing, and soccer are sports associated with the highest injury rates.
People usually experience pain, swelling, and knee instability immediately after the ACL tears. Your knee may buckle or give out on you. You may not be able to fully straighten your knee. You may have difficulty moving your knee and walking. Typically, within a few hours the swelling in the knee increases dramatically.
A physician can evaluate your knee by gathering your medical history, performing a physical examination, and viewing medical images. He or she will ask you about your symptoms and what happened if you were injured and will examine your knee and leg alignment. You will be asked to perform simple movements to help your doctor assess your muscle strength, joint motion, and stability. Your physician will order X-rays to see the condition of the bones in your knee and to identify fractures.
Physical therapy can help restore knee functioning after an ACL tear. Your physical therapist will help you strengthen your knee and special emphasis is placed on exercising the quadriceps muscles on the front of the thigh and the hamstring muscles on the back of the thigh. Eventually, you will learn exercises to improve your balance and coordination. You may need to wear a knee brace during certain activities, which your therapist can help you determine. You will also be educated on how to prevent further injury.