It's not likely Barbaro's condylar fracture was caused by a bad step, but that it caused a bad step itself, which resulted in his secondary fracture below the ankle.

The condylar bone fractures following a process of reforming and flattening in the ankle socket, so to speak, and the process takes place through the heavy pounding of training and racing. This occurs before bones harden to the point that they are fully formed (ie: to young horses for the most part.)

The soft tissue that protects the bone and the ankle wears away prematurely and bone hits bone. A significant period of rest and maturing can save the bones and the horse, but a horse caught up in the Triple Crown is more likely to be encouraged to go on because of the money involved.

Think back to Tale of the Cat, who some vets consider the poster boy of a horse who benefitted from being taken off the track when his condylar issue became apparent. He went on to a very nice career.

The point of this is that a horse with a condylar problem can't hide it. He or she goes gimpy on the sore joint. What is done about the problem is the key. Barbaro was too good and the Triple Crown is there only for 3 year olds, so they hoped to get through the series before his issues worked their way into a bad injury.

Charismatic had the same problem, but racing in California when he did, only a limited number of pain killers were permitted to be administered during his early career. During that period Kentucky was far more permissive and he became a different horse when he was legally medicated for his races there and couldn't feel the bone crushing on bone. The rest is history. He finally fractured the condylar in New York and gave us a preview of the Barbaro incident by a few years.

The aggravated reforming of condylar bones happens to many, many horses and many of them break down. It doesn't take a bad step for this to happen. If you watched the reruns of the Preakness I defy you to spot Barbaro's initial bad step because there wasn't one. He didn't swerve until Prado heard a loud crack and the hind end buckled.

This wasn't about track maintenance or racing luck. This was about covering up a serious condition in the hope that the horse would get through the worst of it. Horseracing is all about hope.