So, the history of ACL surgery goes back 25 or 30 years and has changed somewhat dramatically over that timeframe. In my career, we've gone from multiple incision ACLs to arthroscopically assisted ACLs.
The traditional method would involve either removing a part of the hamstring tendon in the back of the knee or the patellar tendon in the front of the knee. Those tendons would then be replaced ... Those tendons would then be re-routed into the knee to replace the torn ACL. This sometimes requires a larger incision and violation of some soft tissue structures that gives patients problems in the future.
This traditional type of ACL reconstruction then requires drilling full tunnels from outside the bone into the knee.