I doubt very much a doctor would "clear" him to play any more than any doctor probably ever told Ed Reed "nerve impingement in your neck? No problem. Sure you're fine to play NFL football."
What Bens doctor will do is tell him he has a X% chance of injury or death if he plays. Then Tomlin will have the trainer rig up some kind of pad and Ben will accept the risk and he will play.
In short, there are probably NO doctors who would ever recommend playing NFL football with an injury. Seems to me it's entirely up to the player. All the doctor can do is give an opinion, he can't intervene. How many of us do everything our doctors tell us? Not many....