In this Technical Note, we present the surgical technique for primary arthroscopic repair of chronic anterior cruciate ligament (ACL) tears. This approach is indicated for proximal type I and II ACL tears with good-to-excellent tissue quality, characterized by an intact synovial sheath and a simple rupture pattern. Compared with acute ACL primary repair, the most significant challenge lies in the careful mobilization and preparation of the scarred ACL remnant. Notably, chronic ACL tears often present with tissue remnants scarred to the posterior cruciate ligament and/or the femoral notch wall, which may still show favorable tissue quality. With meticulous surgical technique and appropriate patient selection, primary arthroscopic repair of chronic ACL tears may therefore remain a viable option beyond the acute phase. Ultimately, tear location and tissue quality should be the primary determinants for selecting ACL primary repair.
