The anatomy of the knee shares some pronounced similarities with a hinge joint. It is positioned where the end of the thigh bone known medically as the femur connects with the top of the shin bone also known as the tibia. There are four main ligaments that are responsible for the connection of these two bones:

• Medial collateral ligament (MCL) spans the inner part of the knee and act as a means of preventing the knee from bending inwardly.
• Lateral collateral ligament (LCL) spans the outer part of the knee and prevents the knee from bending outwardly.
• Anterior cruciate ligament (ACL) may be found in the middle of the knee. It prevents the tibia from sliding out in front of the femur, and also provides rotational stability to the knee.
• Posterior cruciate ligament (PCL) functions alongside the ACL. It obstructs the tibia from sliding backwards under the femur.

The ACL and PCL intersect each other inside the knee, creating an “X.” formation. This is why they are called the “cruciate” (which means cross-like) ligaments. ACL injuries often materialize correspondingly with other injuries. A classic example of this is when the ACL is torn simultaneously as both the MCL and medial meniscus which is one of the shock-absorbing cartilages based in the knee. This kind of injury quite often manifests in football players and skiers. It has been deduced that women are more likely to have an ACL tear than men. The cause for this is not one hundred percent understood, but it may be as a result of the differences in the anatomy and muscle function of males and females. Adults, in general, tear their ACL in the middle of the ligament or pull the ligament off the femur bone. These injuries cannot heal by themselves. Children are more likely than adults to pull off their ACL with a portion of bone still on it. These injuries may actually heal on their own, or they may need an operation to fix the bone.

When your doctor has any suspicions that you have an ACL tear, an MRI scan may help to confirm the diagnosis. This test may also help to appropriately assess other knee injuries, such as those to the other ligaments or cartilage. Some people have the capability to live as they usually would with a torn ACL. However, most people with the impediment complain that their knee is unstable and may “give out” with any kind of physical activity. ACL injuries that are left untreated may also progress into early onset arthritis in the affected knee.