When England went out to field, the Nottinghamshire man took part in a fitness test in the nets, before going to hospital.
At the close, he appeared on crutches while wearing a protective boot and may now be a doubt for Melbourne.
"I was desperate to get out there and bowl, so I had to try it out in the nets," said Broad, who missed the final three Tests of the
2010-11 tour down under
with a stomach strain.
Tom FordyceChief sports writer at the Waca
"By this stage of a major football tournament a side on the wrong end of successive maulings would be gone before the serious business of the knock-out stage. One bad match is enough to end a tennis player's interest in a Grand Slam; the cut comes as merciful release to the hopelessly out-of-form golfer. Not in cricket. Not on an Ashes tour of Australia, where each additional defeated day serves only to increase the mocking one will receive over the remainder."
"Normally, with a bruise, you'll get a bit of blood to it and get going - and the pain decreases. This actually increased quite a bit.
"Even if there's a small crack there and my symptoms aren't painful, I see no reason why I can't continue to play.
"I've got 10 days until Boxing Day. I see no reason why I can't get myself back in the frame for the Melbourne Test."
Broad has been England's leading wicket-taker with 14 victims and, in his absence, Australia piled on the runs on another desperate day for the tourists.
England, who have not made more then 312 in five innings, are now likely to have to bat for at least five sessions to save the game and avoid surrendering the Ashes by going 3-0 down in the five-match series.
"We've had numerous Tests over the past four years that we've managed to save when we had no right to," said Broad.
"There is a lot of belief in that changing room that we're certainly due a score; there's a lot of guys with great Test records in there, who haven't delivered in this series so far and are desperate to.
Amazing day for Australia - Rogers
"We know, if you keep working hard on your game, things change for you - and we're hoping it does for us in the second innings."
But Australia batsman Chris Rogers, who made 54 on day three, said the deterioration of the Waca pitch could make batting "scary" for England.
"Today was amazing, as good as we have had in the Ashes so far," said the left-hander.
"If these cracks keep widening, it's going to be very hard to bat on - and a little bit scary.
"I think they know, particularly with our pace, that gets a bit worrying."
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