He was rushed to hospital after the training ground accident, where his right leg was put in plaster. He will now face a lengthy spell on the sidelines.
"It is an enormous blow for us to lose a key player this way," Boro boss Steve McClaren told the club's official website.
"We're clearly getting very little luck with injuries, but we have to get on with it." Boro are already without Joseph Job for a few months after he suffered a knee injury.