Isolated injuries to the collateral ligaments (the ligaments on the sides of the knee) can heal with use of protective bracing and a rehab program. Even severe collateral ligament injuries have the potential to be treated non-operatively. Injuries to the cruciate ligaments (ACL and PCL—the large ligaments inside the knee) will not heal and are the ones most commonly associated with reconstructive surgery.

The decision to proceed with a reconstruction is not based on age alone (although the younger the athlete, the more likely they are to want to continue with sports after an injury and are at risk for further injury if the knee remains unstable). An athlete whose sport demands deceleration or direction change usually will not do well if they have abnormal ACL function. Continuing in such sports usually requires a ligament reconstruction surgery. Combined injuries are usually treated by allowing the collateral ligaments to heal and then proceeding with ACL reconstruction. Posterior cruciate injuries are far less common. If seen as an isolated injury, they can often be managed with a muscle rehab program to compensate for the injured ligament.