ANSWER:  The occurrence of a torn anterior ligament alone does not mandate reconstruction. The issue of when to reconstruct a knee ligament depends on an individual’s age, athletic or work demands, ability (and time) to participate in post-op rehabilitation, and the degree of knee instability. The younger the individual (although there is no absolute "upper age limit"), desire to participate in cruciate-dependent sports (those that require deceleration or direction change), frequency of "giving way" episodes, or combined ligament injuries, are indications for ligament substitution. Current surgical techniques (arthroscopic assisted ACL reconstruction) can result in a reasonable substitution for the ligament with less acute recovery time than prior procedures. Overall recovery does require significant rehabilitation; and, while professional athletes may have the time and financial access to rehab on a daily basis (allowing for a very early return to sports), typical return to "at risk" activities is six to nine months post surgery. In your case, with 18 years from injury, additional or secondary injuries to the knee (torn cartilage, arthritis, loose bodies) may account for much of your current trouble and may be addressed with less extensive intervention.