When viewed practically, the human knee is a joint that works like a hinge joint. Anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) are two types of ligaments associated with the knee joint. Both ACL and PCL join the femur to the tibia. They also serve a crucial function of providing stability to the knee joint. The two ligaments are referred to as cruciate because they form an “X” inside the knee. Injuries associated with ACL and PCL are mainly caused by rotational forces exerted on the knee.

Another major cause for ACL injuries is overstretching the ligament. The knee can also suffer an injury when a partial or complete tear occurs on the ACL. There are other ligaments that connect the thigh bone to the shin bone known as the medium collateral ligament (MCL) and the lateral collateral ligament (LCL).

Cruciate injuries occur in most cases when the ACL is torn together with the MCL and the medial meniscus which acts as a shock absorber in the knee. This type of injury is common among people who participate in contact sports like football and among skiers.

For no apparent reason, ACL tear happens more frequently among women than men. This is probably due to anatomical differences and the way muscles function. Among adults the tear usually happens in the middle of the ligament or the ligament is torn off the femur. Such injuries do not heal by themselves. Young children might develop a cruciate injury in which the ACL pulls off with a piece of bone still attached to it. Such injuries will require a surgical operation to fix the bone but in some cases, especially among children, the injury may heal on its own depending on age and severity. If left unattended, cruciate injuries may cause arthritis later in life.