I can somehow see a point in people over a certain age having a certain possibility of carreer ending injuries, if only to limit the players playing on for forever. 
So like players over 32 having a (n+1)*0,1% percentage of the next injury beeing a career ending one, with n beeing the number of overall career injuries. 
                                
                                
                                
                                
                                
                                
                                    Zwei Dinge sind unendlich, die Dummheit und das All...