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Crooked legs and Inflamed Growth Plates in Foals – November 2020

November 1, 2020

Barbara Hunter DVM MS DACVS-LA

Angular limb deformities or ‘crooked legs’ in foals can result from a number of factors. Needless to say, treatment is directed by the underlying cause. Fortunately in many cases, treatment is economic as it consists of rest and dietary management. In some cases, however, treatment requires surgery.

The most straightforward explanation of angular limb deformities is a bend in the foal’s leg, either to the outside or inside of centerline. In newborn foals, the most common reason for this to occur is laxity in the ligaments supporting its joints. This typically responds well to confinement with small periods of controlled exercise (eg: 1-2 hours of turnout) for the first 2-3 weeks of life. In cases were the foal appears immature or has been born prematurely, angular limb deformities can be present due to ‘weak’ or underdeveloped bones within the knees and hocks. These cases are vital to recognize and treat as soon as possible, as delayed treatment can lead to permanent malformation of the limb. The first step in recognition is having a veterinarian examine the foal and take radiographs of the affected joint to ensure that the bones are properly formed.

In slightly older foals (1-4 months old), legs that had started out straight can slowly take on a bent appearance. Most commonly the bend starts at the level of a growth plate just above a joint and is a result of one side of the growth plate growing faster than the other. If this is caught early, the bend is often easily corrected with some simple management changes: corrective farriery, moderate confinement and minimizing supplemental feeding. In cases where the bend is severe, or the foal is near the age when the growth plate closes, rapid correction is essential. Once the growth plate closes, the opportunity for the slower growing side of the limb to ‘catch up’ and straighten the leg has been lost. These are the types of cases that require surgical correction. Particularly in cases of fetlock angular limb deformity, where the affected growth plate closes between 12 and 16 weeks of age, correction of the deformities early in their development is important to achieve a good result.

Physitis or inflammation of growth plates does not cause deviation of a limb, but it can cause lameness and unsightly swelling of growth plates. This is most commonly seen in weanling to yearling aged horses, particularly during periods of rapid growth. Treatment is geared toward slowing growth and decreasing pressure on the limbs. Affected horses should be confined and controlled exercise minimized. It is important to decrease their plane of nutrition both to slow growth and encourage some weight loss. Finally, treatment with systemic anti-inflammatories, such as phenylbutazone, is important in the short term to decrease the inflammation within the growth plate.