ACL reconstruction is surgery to replace a torn anterior cruciate (KROO-she-ate) ligament (ACL) — a major ligament in your knee. ACL injuries most commonly occur during sports that involve sudden stops and changes in direction — such as soccer, football, basketball and volleyball. What does ACL surgery do? ACL reconstruction is surgery to reconstruct the ligament in the center of your knee. The anterior cruciate ligament (ACL) connects your shin bone (tibia) to your thigh bone (femur). A tear of this ligament can cause your knee to give way during physical activity, most often during side-step or crossover movements.