Tearing the ACL, or anterior cruciate ligament, in the knee is an injury common to sports participants. The treatment typically involves surgical reconstruction of the tissue, and then the patient must pass a physical skills test to return to participation on the field or court. A recent review of research conducted in Australia raised the question of whether these tests are valid measures. Researchers found that players who passed the test were just as likely to reinjure their knee as those who did not. And the likelihood that they would go on to tear the ACL in the other knee rose by 235 percent. Dr. Albert Gee, orthopedic surgeon with the Sports Medicine Center, explains why more research is needed to understand ACL injuries and what people can do in the meantime to try to prevent the trauma from happening in the first place.