ACL Injury Facts

Anterior cruciate ligament (ACL) injuries are caused by a sudden twisting of the knee. The anterior cruciate ligament (ACL) is located in the center of the knee. It limits rotation and the forward movement of the tibia, or shin bone. Learn more about ACL injury ›

Ligament Injuries to the Knee

There are four major ligaments in the knee. Ligaments are elastic bands of tissue that connect bones to each other and provide stability and strength to the joint. The four main ligaments in the knee connect the femur (thighbone) to the tibia (shin bone), and include the following:

  • Anterior cruciate ligament (ACL) - the ligament, located in the center of the knee, that controls rotation and forward movement of the tibia (shin bone).

  • Posterior cruciate ligament (PCL) - the ligament, located in the back of the knee, that controls backward movement of the tibia (shin bone).

  • Medial collateral ligament (MCL) - the ligament that gives stability to the inner knee.

  • Lateral collateral ligament (LCL) - the ligament that gives stability to the outer knee.

Learn more about ligament injuries to the knee

Treating Anterior Cruciate Ligament (ACL) Injuries

The ACL (anterior cruciate ligament) is a band of tough, fibrous tissue that stabilizes the knee. Injuries to the ACL are very common, especially among athletes. Treatment for your injury may or may not involve surgery. Treatment depends on the severity of the injury and how active you hope to be in the future. Your healthcare provider can discuss your treatment options with you.

Reduce Pain and Swelling

Whether or not you have surgery, you can help reduce pain and swelling with rest, icing, and elevation. Rest with your knee elevated above heart level. Put ice on your knee 3-5  times a day for 10-15 minutes at a time. (Keep a thin cloth between the ice and your skin.) Take any medications that are prescribed. And follow any other instructions you’re given.

Learn more about treating ACL injuries

Thermal Shrinkage for Anterior Cruciate Ligament (ACL) Repair

The ACL is a band of tough, fibrous tissue that stabilizes the knee. Injuries to the ACL are very common—especially among athletes. Most often, the injury occurs when the knee is forced beyond its normal range of motion. This can stretch or tear the ligament, much like the fibers of a rope coming apart. You may have pain and swelling and feel like your knee “gives out.” A treatment called thermal shrinkage can help repair the ACL.

Thermal Shrinkage Therapy

Heating parts of the ACL causes them to shrink. This tightens the ligament and allows it to better stabilize the joint. Thermal shrinkage is done during an arthroscopic procedure. A long, thin lighted tube called an arthroscope is used to see and operate inside the knee.

Learn more about thermal shrinkage for ACL repair

Tips for Preventing an ACL Knee Ligament Injury

The knee is a joint where three bones join: the femur, or thigh bone; the tibia, or shin bone; and the patella, or knee cap. Four ligaments attach to the femur and tibia and give the joint strength and stability. One of these, the anterior cruciate ligament (ACL), is in the center of the knee and limits rotation and the forward movement of the tibia. Recent studies estimate that nearly 250,000 ACL injuries occur annually in the United States.

The ACL is most often stretched or torn (or both) by a sudden twisting motion - when, for example, your feet are planted one way and your knees are turned another. You can also injure your ACL by quickly changing the direction in which you're moving; by putting the brakes on too quickly when running; or, if you're a woman, when landing from a jump. A woman's body structure and hormones cause more force on the ligaments, increasing the likelihood of injury.

Learn more about preventing an ACL injury

Knees Are Casualties of Women's Sports

Active women are at least twice as likely to suffer serious knee injuries as men, but it's not just athletes who are at risk.

Although female athletes at the high school and college level suffer serious knee injuries, women who play recreational volleyball or participate in step aerobics also can injure their knees, says the American Academy of Orthopaedic Surgeons (AAOS). A mother who carries her child down a flight of steps and misses the last step also can injure her knee. In short, a knee injury can happen to any woman, no matter how athletic she is.

The chief movements that cause knee problems in women are pivoting and turning, the AAOS says.

Learn more about knee injuries and women's sports

Your Guide to ACL Injuries


Take a Personalized Health Test