An NFL panel found that certain knee and ankle injuries happen more often in games played on artificial turf than on grass. The league's Injury and Safety Panel is presenting its study at the annual meeting of the American Academy of Orthopaedic Surgeons in New Orleans on Friday. The report examined the 2002-08 seasons, comparing games played on grass to those on FieldTurf. It was found that the rate of ACL injuries was 88 percent higher in FieldTurf games -- a conclusion the manufacturer of the synthetic field hotly disputes.