DB is right, Seabiscuit ruptured a tendon, recovered, and went on to race. I'm no expert, but I've heard that horses have been bred to have finer bones for more speed. I know that some breeds of dogs have been bred to accentuate certain features and it's gone to the extreme. Some smallish breeds with large heads have to have a C-section in 100% of cases. I've heard that if you get a bulldog that can walk up the stairs, you are very fortunate.

I've also heard that the horses raced harder at a younger age. I heard that all thoroughbreds born during the year are given the birthdate of  Jan. 1st, so the horses aren't exactly three yr. olds. Stress like that on fine bones that haven't had a chance to mature can cause them to shatter. I also understand that every horse in the Kentucky Derby has the same horse (forgot which one) in it's pedigree, so the gene pool is kind of small.

As for the people copying and pasting celebrity news, etc. I'm an even bigger naive idiot than I thought for believing that they were actually typing those stories! I never thought of the plagarism angle either.