Patella Infections in Foals Require Prompt Care (AAEP 2011)

Call the vet, or wait and see? When concerned about a foal's health--particularly when infections are suspected--waiting is never a good idea. Osteomyelitis in young foals, for instance, requires immediate treatment, as Alastair Kay, BVSc, MS, Dipl. ACVS, MRCVS, equine surgeon at Minister Equine Clinic, in North Yorkshire, U.K., relayed at the 2011 American Association of the Equine Practitioners convention, held Nov. 18-22 in San Antonio, Texas.

"Osteomyelitis is an infection of either bone or bone and cartilage combined," Kay explained. "If infection develops in bone and/or cartilage close to joints, the chances of achieving a high-level athletic exercise may be poor, particularly if the infection is aggressive, a large area is involved, or if treatment is initially delayed."

Osteomyelitis is relatively common in young foals less than 4 weeks old, and it can affect all bones of the skeleton. Long bones such as the cannon bone, small bones such as in the lower hock or knee joints, or bones within the foot are most commonly affected.

"Infection of the patella (equivalent to the knee cap in humans) is uncommon in foals, but when it happens can result in prolonged and severe stifle joint infection," added Kay.

Foals with osteomyelitis of the patella often present with swollen stifle joints and lameness. Veterinarians can base an infection diagnosis on radiographs (X rays) of the stifle and joint fluid analysis, and they can treat affected foals in the hospital by flushing the infected stifle, injecting the joint and patella with antibiotics, and administering systemic antibiotics (intravenously or orally).

Because the treatment, management, and outcome of patellar osteomyelitis have not been described in significant numbers, Kay and colleagues from Hagyard Equine Medical Center (Lexington, Ky.), The Ohio State Medical Center (Columbus), and Rossdale's Equine Hospital (Newmarket, U.K.) searched their medical records from 2003 to 2007 and identified eight foals with evidence of patella osteomyelitis. Foals with both short- and long-term (i.e., more than 15 months out) follow-up data were included.

Key findings of the study were:

  • Six of the eight foals survived long-term (again, more than 15 months);
  • Six foals were sound and sold as yearlings, as show or racehorse prospects;
  • Two of eight foals remained lame (following treatment that did not include direct injection of the patella) and died of additional causes.

"All foals presented to the clinic that had been lame for between two and days, and six of eight of these foals had received antibiotics prior to referral," he noted. "Only the foals that had direct injection of the patella lesion survived. Also, all foals had the stifle joints lavaged to rid the joint of infection, so joint treatment needs to be combined with the patella injection to maximize the outcome.

"Based on this retrospective analysis of the available data, prompt treatment can result in a sound foal that is still eligible for an athletic career," concluded Kay. "Systemic bacterial infection or other disease that occurs around the time of birth will likely prolong the treatment and recovery periods."

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.