Barbaro is no longer bearing weight on the right hind leg he shattered eight months ago in the Preakness Stakes after undergoing surgery on Jan. 27, 2007, to place two steel pins through a bone.
The biggest fear is that the bone bearing the weight can break. Doctors said the surgery went well.
Doctors treating Barbaro in Chester County said they will continue to treat the horse aggressively "as long as he remains bright, alert and eating."
This is the first time in weeks the right hind leg has been the focus of concern. For months, it was the left hind leg that put Barbaro's recovery in serious jeopardy because of laminitis, the often-fatal hoof disease.