Hamm, 25, broke his right hand during a competition in May and injured his rotator cuff while rehabilitating his hand. He said the hand wasn't sufficiently healed and, with the rotator cuff injury, he wasn't healthy enough to compete in the Beijing Olympic Games.
"I have put my heart and soul into my comeback and done everything I could to get ready in time to compete in Beijing," said Hamm. "After returning home from the preparation camp, I had a few physical setbacks and it became clear to me that my physical preparations would not be sufficient to properly represent the United States and contribute to the team's efforts to win a medal."
Hamm won the all-around gold medal in Athens, Greece, four years ago in the closest event competition in Olympics history. He had appeared in three meets, not counting the event in which he was injured, in 2008, winning the all-around in each.