One of the most common knee injuries is a ligament tear (tehr), primarily, the anterior cruciate (KRUE-shee-ate) ligament, or ACL (A-C-L), which may require reconstructive surgery. Once torn, the ACL ends are usually shredded and don't have the capacity to regenerate or heal, despite any efforts to sew the torn ends together. Reconstruction is necessary to repair the ligament correctly, using a strip of hamstring tendon from the patient's own leg to replace the damaged ligament. The tendon strip is stabilized at both ends with staples or screws. Within six to eight weeks after the surgery, the tendon graft begins to remodel and form a new ligament; however, proper care must be taken to avoid stressing the ligament during this time or the reconstructed ligament may rupture or loosen. In most cases, surgery is performed by arthroscopic (are-throw-SKAW-pik) methods and requires an overnight stay at the hospital. Immediate protected weight bearing is allowed, but with a hinged knee brace and crutches for support. Rehabilitation may begin immediately and can last from six to nine months.