Epiphysitis (Physitis)

Long bones like the cannon bone are divided into the ends (epiphyses) and middle shaft (diaphysis) and in young growing horse these areas are separated by the growth plate or epiphyseal plate. This cartilage plate is where new bone growth extending the length of the bone occurs.

Epiphysitis results from disturbance to the normal pattern of growth and maturation in the plate including conversion of cartilage into bone (ossification). This causes a firm painful swelling around the growth plates and flaring of the ends of the affected long bones. Heat in affected areas may be apparent and foals may be reluctant to move and exercise normally. The usual age of occurrence is 4-12 months, but it can occur up to 2 years of age.

Causes include rapid growth, high energy intake, obesity, mineral or trace element deficiencies and imbalance, poor hoof conformation and trauma e.g., from excessive exercise. Physitis is part of the Developmental Orthopaedic Disease complex.

Treatment: many cases resolve spontaneously with no treatment. The plane of nutrition should be reduced by reducing energy intake to moderate the growth rate and any mineral issues should be corrected. Some foals may require corrective foot trimming or shoeing to counter limb deviations. Surgical treatment involving bridging the growth plate may be appropriate in some severe cases. Veterinary advice should be sought.

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