Can the ACL heal itself?

No unfortunately the ACL cannot heal itself. This has been shown with many histological studies and MRI based studies over many years. There are two powerful forces that work against ACL healing namely knee kinematics and the release of tissue plasminogen immediately after the injury. Both the knee movement and this particular enzyme prevent ACL healing. Even if we put your knee in a brace or cast to prevent movement, we can not prevent the release of the enzyme into the knee which happens almost at the same time as the injury itself.