Your anterior cruciate ligament, or ACL, is one of the four ligaments that connect the bones in your knee joints. The ACL is also one of the most injured ligaments in the knee. According to the American Academy of Orthopedic Surgeons, an estimated 200,000 ACL injuries occur every year. The injury results from overstretching of the ligament, either due to a non-contact or contact action. Most often, ACL tears occur during athletic activity.
Ligament Basics
Ligaments are strong structures that are comprised of connective tissue. Your body uses them to stabilize joints by connecting bone to bone. In the case of your ACL, the tendon connects your tibia to your femur at your knee joint. Ligaments, unlike muscles, do not have the ability to contract and they are less elastic in nature. This makes ligaments prone to tears when overstretched.
Your ACL
Your ACL crosses in front (anterior) of your posterior cruciate ligament (PCL) in the center of your knee, hence the name cruciate, which comes from the Latin word for cross. Together, the two ligaments control the backward and forward motion of your knee. Specifically, the ACL is responsible for restraining the forward motion of your tibia in relation to your femur. Your ACL is also responsible for limiting the inward twisting or rotation of your knee. Your ACL provides almost 90 percent of the stability to your knee.
Causes of ACL Tears
Approximately 70 percent of ACL tears are the result of non-contact actions, while the remaining 30 percent are caused by direct contact, such as in collisions. Common causes of ACL tears include rapid direction changes, sudden stops, deceleration during running, landing incorrectly from a jump, hyper-extension and collisions with other players. Often, ACL tears are the result of planting your foot and cutting in a different direction. If the traction of your foot with the ground does not give, your upper leg and body can rotate and tear your ACL.
Activities with High Tear Risk
Because your ACL becomes stretched tight when your lower leg rotates inward, activities that involve frequent plant and twist motions pose a high risk for tearing your ACL. Sports where this type of movement is common include football, tennis, basketball and soccer. Activities that involve jumping, such as gymnastics and track and field, also provide the potential for ACL tears. Finally, sports that involve physical contact can produce ACL tears.
Treatment
Immediate treatment of your ACL tear involves resting your knee, using ice to reduce swelling, applying compression with an Ace bandage to minimize swelling and elevating your injured knee. In many cases, your injury can be treated with progressive physical therapy and rehabilitation. However, your ACL tear may require surgery. ACL tears cannot be repaired by stitching the two ends of your torn tendon together. Rather, your surgeon will substitute a new tendon from elsewhere in your body, typically a part of your patella tendon, hamstring tendon or quadriceps tendon. Reconstruction surgery has become highly successful, with the vast majority of athletes returning to their pre-injury performance levels.
References
- American Academy of Orthopaedic Surgeons: Anterior Cruciate Ligament Injuries
- American Academy of Orthopaedic Surgeons: ACL Injury - Does It Require Surgery?
- EHealth MD: What Is the Anterior Cruciate Ligament?
- EHealth MD: What Causes An ACL Tear?
- Medline Plus: Anterior Cruciate Ligament (ACL) Injury
- Athletic Advisor: ACL Tears
