This may be necessary if a previously reconstructed ACL graft is reinjured and ruptured, but may also be necessary if previous surgery has been performed suboptimally causing a failure to stabilise the knee or restriction of movement. Careful assessment of the individual case is necessary, and if a re-do procedure is required, this can sometimes be performed in a single operation. Sometimes, however, two surgical procedures are required. If the hamstrings were not used in the original procedure, we are usually able to use these as a graft. If they have been used previously we prefer to use a graft from the tissue bank.