The 31-year-old slugger will undergo surgery within the next week or two and is unlikely to recover in time to participate in the first half of the 2012 regular season. He might even miss the entire year.
The news arrives with awful timing for the Phillies, who had their dreams of a World Series title dashed this week by the Wild Card-winning Redbirds.
Howard, a .275/.368/.560 career hitter, is owed a whopping $125 million over the next five seasons.
The Phillies also announced Saturday that Cole Hamels needs minor surgery on his left elbow.