According to the actor's publicist, the star has smashed his metatarsal - the same injury that has prompted his soccer hero David Beckham to pull out of the upcoming World Cup.
Ironically, Monaghan was sympathising with Beckham on U.S. TV a month ago, when he told chat show host Jimmy Kimmel he really felt for the English soccer legend.
He told the host, "I'm a big Beckham fan; he's a Manchester United legend. Obviously I was pretty heartbroken that he got hurt the other night... He's my age... but, as a footballer, it's gonna be tough for him to come back.
"We're all hoping that he will. He's such an ambassador for the sport... and he's a handsome devil as well."
Monaghan made his first outing since breaking his foot to pick up antique furniture in West Hollywood for his Los Feliz, California home on Friday (09Apr10).
An eyewitness tells WENN, "He was struggling with every step. He was obviously in a lot of pain."