The posterior cruciate ligament (PCL) is one of two ligaments that criss-cross inside the knee. Both of these ligaments have different functions to allow joint movement while stabilizing the knee.
Without the PCL, the tibia (lower leg bone) doesn't move normally. It slides back too far when the knee is straight. And it doesn't glide forward as it should when the knee is bending. More recent studies also show the PCL helps hold the knee steady side-to-side as well.
Many people are able to function just fine without the PCL for everyday activities. But the risk of re-injury or another injury is raised when patients participate in sports or other vigorous activities.
And long-term studies show that over time, abnormal shifting and sliding of the tibia leads to degenerative arthritis of the joint. This happens because the places where the bones come together and move against each other have changed. When the joint surfaces don't match up properly, uneven wear occurs.
You can always get a second opinion. But experts agree that early reconstruction is the treatment of choice for PCL injuries. There's no guarantee, but the hope is that by restoring stability, degenerative joint changes leading to a painful arthritic condition can be prevented.