An ACL autograft is a reconstruction of the anterior cruciate ligament using tissue obtained from the same patient.
The biological advantages of autograft
Although harvesting autograft material from the patient leaves them with a harvest site that may be a bit compromising, autograft has the advantages of being genetically identical to the tissue it is replacing, it is not treated with any chemicals or physical processes and it is warm and fresh. In the case of the ACL it will still need, however, to re-establish a blood supply and re-fashion itself to fit its new purpose.
Autograft versus allograft in anterior cruciate ligament reconstruction. Kan S-L, Yuan Z-F, Ning G-Z, Yang B, Li H-L, MD, Sun J-C and Feng S-Q. Medicine (Baltimore). 2016 Sep; 95(38): e4936.