Epiphysitis in Horses - Physitis in Young, Growing Horses

Four month old filly has developed epiphysitis. Fitting her up for a fall futurity and she has developed two epiphysitis bumps on her front ankle. Getting tender. Taken the second crop hay away and reduced the grain intake. Her show is in five days, what are your suggestions? SW, Wisconsin

Dear SW,

I went ahead and titled this entry “epiphysitis” even though the experts prefer the term “physitis.” The epiphysis is the very end of a long bone while the physis is the actual growth plate, and that sounds like the problem in your filly.

The terms refer to inflammation of this growth plate, which appears as warm, painful swelling near the end of long bones such as the cannon bone, the radius and the tibia. Physitis–along with angular limb deformities, subchondral bone cysts, osteochondrosis, flexural limb deformities and cervical vertebral malformation (Wobbler’s)–is considered a general growth disturbance of young horses or developmental orthopedic disease (DOD).

You’ve done the right thing by reducing your filly’s grain, since overfeeding (especially energy) is one of the leading causes of physitis. I recommend you work with your veterinarian to analyze your hay and the rest of her diet to make sure she’s getting the appropriate balance of calories, protein, and minerals for her age, breed and size. It’s especially important to make sure the calcium:phosphorus ratio is correct and that she’s getting sufficient amounts of copper, zinc and some other trace minerals.

Vigorous exercise is another risk factor for physitis but complete stall rest isn’t ideal for a young horse either. Ask your veterinarian how much turnout your filly should get now while her growth plates are flared up and later after she’s recovered. Breed or genetics is another risk factor for developmental orthopedic diseases, but that’s out of your control.

It’s unfortunate that you have to miss your show, but better to get this condition under control now by adjusting your filly’s diet and exercise than have a surgical problem on your hands or worse yet, a permanent unsoundness that may prevent her from being ridden later.