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Epiphysitis in Horses

Epiphysitis, also known as physitis, is a generalized bone disease of young, growing horses that is characterized by the enlargement of the growth plates in long bones such as the tibia, radius, and cannon bones. It is most commonly seen in horses four to eight months of age, when they are undergoing rapid growth, but can be seen in slightly older foals as well, even up to two years old. While the exact cause of this condition is unknown, fast-growing overweight young horses that are fed high calorie diets are at highest risk.

Symptoms and Types

Epiphysitis causes an enlargement of the physes (growth plates) at the end of long bones such as the radius, cannon bone, and tibia. This swelling makes the ends of the bones appear as an hourglass. Other symptoms of epiphysitis include:

• Joint pain
• Joint swelling
• Inability to stand (when severely affected)

Causes

The exact cause of epiphysitis in horses is unknown; however, foals with excessive musculature on a high plane of nutrition are at higher risk. The cause is likely multifactorial and not the same for every case. In this condition, there is a problem with the cartilage at the growth plate and it is incapable of undergoing the normal transformation into bone, a process called ossification. This problem results in inflammation around the affected joint.

Diagnosis

Clinical signs in conjunction with radiographic findings of the affected joints will lead to a diagnosis of epiphysitis in a growing horse.