The horse would fracture his leg on the 11th hurdle but if you needed proof that Synchronised wanted nothing to do with this race, this should suffice.
If you need more evidence, here's Synchronised unseating McCoy.
EDIT- We've received a some just criticism on Twitter that Synchronised stopping before the fence is quite common. Taking all that criticism on board, it doesn't change the larger point that there are signs Synchronised was clearly irritable before the race. Horses can't speak for themselves, but I think it's fair to say that the horse didn't want to run the race. Horse racing experts can and should disagree. That's just one layman's opnion.