ACL reconstruction is surgery to replace the anterior cruciate (KROO-she-ate) ligament (ACL) one of the major ligaments in your knee. ACL injuries most commonly occur during sports that involve sudden stops and changes in direction; such as basketball, soccer, football and volleyball.A torn ACL can't be successfully sewn back together, so the ligament is replaced with a piece of tendon from another part of your leg or from a deceased donor. This surgery is usually performed through small incisions around your knee joint. A narrow, fiber-optic viewing scope is used to guide the placement of the ACL graft.