Does anyone know why House's ball is so prevalent throughout the show?

Throughout the show, House's gray and red felt ball is seen many times, but it feels like it is focused on more than a prop should be. Wilson says "that ball saves lives" as a joke to cuddy. In episode three of season six there is a cinematic shot of the thing as Foreman takes the tarp off of House's desk once he gets the head of the department job. Is it supposed to be a metaphor for something or is it just a prop that the people behind the scenes liked using?