The anterior cruciate ligament--or ACL--is a major stabilizer of the knee joint. When this ligament is torn, the original, damaged tendon is removed, and the knee is reconstructed with new tissue. Typically, surgeons cut a strip from the patellar tendon (below the knee) to replace the ACL. Or they may use tissue from one of the hamstring tendons along the inside of the thigh. Screws are used to attach the new tissue in the exact location of the original tendon.

This procedure is typically successful. In a recent study of 200 patients, no significant medical complications developed from ACL reconstructions using the patellar tendon. In fact, 96 to 98 percent of patients said they would choose this surgery if they had to go back and do it again.