When the graft tissue is inserted into the knee, it begins to grow a new blood supply. New cells migrate into the tissue and begin to repair and remodel the graft. Therefore, an ACL graft is nice and strong when it is first surgically implanted. However, initially the knee is weak and the reflexes impaired. As knee function improves and the patient’s confidence increases, the graft begins to degenerate and actually becomes weaker. The ‘danger zone’ is between 3 to 9 months. As the graft develops a new blood supply within the knee after surgical reconstruction, the new cells remodel the graft and it becomes stronger.