Are steriods illegal in AERC?

["guest@endurance.net" <guest@endurance.net>]

Kristi iluvdez@yahoo.com
To make a long diagnostic story short, the vet was here 
yesterday and injected my horse's hocks with Depo-Medrol
(methylprednisolone acetate - a corticosteriod). She rides
3-day eventers and swears this is the best thing she's seen
for bone spavin. I have to give my horse a few days paddock
rest before riding him, so I haven't seen if the stuff is a 
miracle drug for him or not. My question - is this a 
banned substance in AERC (??). I'm wondering, because when I posted a month or so ago for advice on treating arthritic hocks, there were lots of mentions of Adequan, Legend, etc, but none on steriods...I was a little leary about using steriods (I read WAY too much sometimes, I think), but since my very caring, knowlegeable vet uses it on her own beloved horse, what more of a recommendation could I ask for! If using this means I can't compete, so be it, 'cause I only want my best buddy to be happy
and comfortably sound...Kristi