Television replays showed his foot pointing in the wrong direction and he was eventually taken off on a stretcher, with Broadfoot in obvious distress.
Related ArticlesFerguson: Antonio Valencia is out for seasonManchester United 0 Rangers 0Champions League actionPremier stars face a big test in keeping upStiles to sell World Cup medalSport on television"I'm not too sure what happened," he admitted. "I just slid in and looked round and his bone was sticking out. We tried to get the physio on to help him because you don't like to see that.
"These things happen and hopefully he makes a fast recovery. I've never seen anything like that so close before.
"You see things like that on television and it's not good but to see it there in front of you, it doesn't look nice and I just hope he recovers quickly."
Sir Alex Ferguson, the United manager, revealed after the goalless draw with the Scottish champions he fears Valencia will be out for the rest of the season.
"It is a dislocation or a fracture and he gets operated on tomorrow [Wednesday] morning," he said. "It was an innocuous challenge but when you saw the Rangers player waving, you knew it was a bad one.
"It is a bad blow for the boy. It is similar to the injury Alan Smith got and you are talking about the rest of the season."
Broadfoot was deployed in an unfamiliar left-back role as manager Walter Smith opted for a packed five-man defence.
The game-plan paid off, with Rangers by far the happier team as they returned to Ibrox with a point from their Champions League opener.
Broadfoot said: "I played in pre-season in that position so I knew what my job was, I knew the game-plan and I just stuck to my game-plan.
"We are just delighted to come to Old Trafford and get the point to be honest. It does feel like a win because not a lot of teams come here and get a point so we are delighted.
"We deserve credit for coming to Old Trafford and getting a point because not many teams do that. I'm sure if you were to ask any team in the Premier League, they would be delighted to come to Old Trafford and get a point.
"People might say it's negative but we had chances to win the game, albeit it not as many as them, and we are happy with the point."