Penning a touching message to fans and the city of Chicago, Miller said "the time has come."
"It has been an incredible journey for myself and my entire family and we can’t thank you enough for your continued support," he wrote. "I would love more than anything to step on Soldier Field one last time but I physically cannot give the game and our fans what they deserve."
The Bears had signed Miller a one-year contract last June. The deal was at least a goodwill gesture for a popular player who dislocated his knee trying to make a touchdown catch during a game at New Orleans. He has undergone nine surgeries since then, but was walking on his own by late-December.
"It’s difficult to find words to express my love and gratitude to every single person that has cheered my name, picked me up and stood strong with me throughout my time in this league. I am forever grateful," he wrote. "To the McCaskey Family and the entire Bears organization, THANK YOU for changing my life! To my Family, teammates and coaches, I value nothing more than the friendships and love I have gained from this game! I love you all!
"And to everyone else chasing a dream... never stop, never settle!"