Veterinarians commonly inject horses’ joints both to diagnose and treat lameness. They inject diagnostic anesthesia to pinpoint painful joints, and they inject anti-inflammatory medications to help treat them. These procedures, however, don’t come without risk of infection, so most veterinarians (about 78%, according to a 2009 survey) add antibiotics to intra-articular (IA) injections just to be safe.

"The most feared complication is infectious arthritis," said Anna Bohlin, DVM, of the Evidensia Equine Hospital, in Sweden, "and to some veterinarians this justifies routine use of prophylactic (preventive) antibiotics."

But are these additional drugs really necessary?

To find out, Bohlin reviewed veterinary records from horses treated with joint injections from 1999 to 2010 and their outcomes. She presented her findings at the 2014 American Association of Equine Practitioners Convention, held Dec. 6-10 in Salt Lake City, Utah