Angular Limb Deformity in the Foal

This picture shows a horse with a fetlock varus angular limb deformity. The part of the leg below the level of the fetlock or ankle is rotated in. There is a hoof wall extension on the outside of the foot to help correct the fetlock varus angular limb deformity. (Courtesy of Imprint Equine Hoof Care)
This picture is a radiograph of a foal’s knee. The lines on the radiographs are drawn through the center of the radius and cannon bone. Where the lines intersect tells the veterinarian where the angular limb deformity originates and where surgery needs to be performed. (Courtesy of Lauren Lamb)

By Lauren Lamb

Every year thousands of foals are born in the United States. Most of these foals are bred and raised to have a job (racehorse, show horse, ranch horse, etc.). Good limb confirmation is critical to ensuring that a horse can perform its job at the highest level possible. Establishing proper limb confirmation in a horse starts in the first few weeks of life.

Angular limb deformity is the term used to describe a foal with crooked legs. A foal can have a valgus deformity, where the leg is rotated outward, or a varus deformity, where limb is rotated inward. Most angular limb deformities are located at the carpus (lower radius). Many deformities can also be seen in the fetlock (lower cannon bone) and hock (lower tibia).

Angular deformities can be congenital (foal is born with deformity) or acquired (develops over time). Angular limb deformities can be secondary to malposition within the uterus, exposure to toxin during pregnancy, poor nutrition or trauma to a growth plate.

Foals can also develop an angular limb deformity if they are premature or dysmature at birth. A premature or dysmature foal will have bones in the knee and hock that are soft and not mineralized. Weight bearing on these soft bones will cause them to be crushed and result in an angular limb deformity. Over use is another cause of an angular limb deformity. A foal may over use a limb secondary to a lameness in the opposite limb.

Most foals are born with a mild degree of angular limb deformity. This deformity is usually secondary to laxity in the tendons and ligaments. This laxity should resolve within the first two weeks of life. If the horse continues to have an angular limb deformity beyond two to three weeks of life, treatment may be needed to correct the angular limb deformity.

Timing is key when treating a foal with an angular limb deformity. Veterinarians rely on growth of bone to correct angular limb deformities. A deformity located in the fetlock region needs to be addressed prior to 60 days of age; there is minimal growth in the bones around the fetlock beyond 60 days of age. A deformity in the knee or hock can be addressed between three and 12 months of age. Growth in the knee and carpus decreases significantly after 12 months of age.

Learn more about angular limb deformity in the foal in the April issue of OKFR!