the face of a normal clinical evaluation on service entrance . In addition , if the presumption of soundness is rebutted , the Veteran is entitled to a further presumption that the disability not noted on entry in ( but manifested during ) service was aggravated by service . This presumption likewise can be rebutted only by clear and unmistakable evidence ( of non - aggravation ) . The presumption of soundness applies only where there is evidence that a disease or injury was not noted upon entry into service manifested or was incurred in service . Once the presumption of soundness is applied , if the Secretary is unable to rebut the presumption , the disease or injury that manifested in service is deemed incurred in service