As Steve notes: Two doctors on Mr. Cheney's medical team said they would be willing to discuss his case with this physician-reporter if given permission to do so. But the White House declined to grant such permission.
This kind of stuff only fuels rumors. If it's a routine procedure than what's the fuss? Cheney's health has always been out in full view for the public to see, but his knees are deemed "super-duper-super-secret"