The knee joint is made to withstand the forces of walking, running and jumping as well as allowing motion. The knee is basically a hinge joint made of bone, ligament, and cartilage.

The anterior cruciate ligament or ACL is attached to the femur bone and tibia bone. The major function of the ACL is to provide stability to the knee during cutting and jumping activities. An ACL tear is a major problem for an athlete who desires pivoting, cutting and changing direction as part of their athletic lifestyle. These functions are required for sports such as skiing, soccer, football, basketball, volleyball and racquet sports. Once the ACL is torn, the knee becomes unstable and there is a risk of repeat injury and over time possibly advanced degeneration of the joint (arthritis).

The posterior cruciate ligament or PCL is one of the most important ligaments of the knee, giving it stability. The PCL achieves this role by preventing excessive twisting, straightening of the knee (hyperextension) and backward movement of the tibia on the femur.

When these movements are excessive and beyond what the PCL can withstand, tearing to the PCL occurs. This condition is known as a PCL tear and may range from a small partial tear resulting in minimal pain, to a complete rupture of the PCL resulting in significant pain and disability.