In most cases, ACL reconstructions are not done immediately after injury. Most surgeons will wait several weeks. Operating too early can result in knee stiffness after surgery. Waiting a few weeks allows the swelling to subside and the knee to achieve full, pain-free movement before the operation.
If you are less active, your doctor may delay surgery even longer in order to determine the degree of knee instability or to let you schedule the operation at your convenience. In such cases, your doctor may restrict your activity in order to prevent injuries to other parts of the knee, such as the meniscus.
However, if an ACL tear occurs along with a certain type of meniscal tear or other knee injuries, surgery may need to be performed sooner.