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.

The 2,833 records revealed that veterinarians injected 14,124 joints in horses ranging from 4 months to 24 years old. Of those joints, 40% were treated with anti-inflammatory medications, 30% with diagnostic anesthesia, and 30% with both anti-inflammatories and anesthesia. The most commonly injected joints were the coffin, fetlock, and stifle joints.

Veterinarians injected 96% of the joints they treated with corticosteroids; 49% with hyaluronic acid; and 7% with polysulfated glycosaminoglycan (PSGAG).

If a horse developed an infection within 60 days following joint injection, Bohlin considered it a case of infectious arthritis. She identified infectious arthritis in 16 h