Now that we’re gearing up for foaling season, it’s time to start reminding ourselves about crooked legs; how, when and why to correct them.  Angular limb deformities may occur secondary to a congenital/inherited defect or acquired with growth from various external factors such as exercise, nutrition, infection and abnormal weight bearing.  Deformation ultimately occurs when growth across the entire physis (growth plate) is unequal resulting in subsequent uneven growth of the bone.

Valgus (lateral deviation) or varus (medial deviation) deformities are a common occurrence in foals.  Naming of these deformities is determined by location of the joint immediately above the deviation.  For example, the most common angular limb deformities are carpal valgus (“knock kneed”) followed by tarsus valgus (“cow/sickle hock”) and fetlock varus (“pigeon toe”).

In addition to angular limb deformation, concurrent rotational deviation of the limb can occur.  It is most common to see outward rotation with valgus deformities and inward rotation with varus deformities.

Evaluation of foals for angular limb deformities should be completed by your veterinarian at the farm or in the clinic, with both subjective visual assessment while standing and walking and objective radiographic assessment.

Radiography of the joint should be performed to determine if the deformity is caused by malformed/crushed bones, to measure the degree of angulation from normal to help aid in determining degree of correction in the future and to assess for any further joint/bone damage that may make correction and prognosis more complicated.

Many mild angular limb deformities can “self correct” given time with conservative management including exercise restriction and corrective hoof trimming +/- glue-on shoes with appropriate extension applied depending on the limb deformation.  Glue-on shoes should be changed at least every 14 days to account for the rapid growth that foals have.

Conservative management has to be balanced with the age of the foal and growth potential for the affected bone(s) as minimal growth occurs in the lower growth plate of the cannon bone after 3 months or the lower growth plates of the radius and tibia after 6 months.

Surgical correction should be used early in moderate to severe cases, or in those foals in which conservative management does not correct the deviation.  Surgical treatments recommended by your veterinarian based on the type and severity of the deviation includes:

1.       Growth acceleration: Periosteal transection and elevation (“periosteal stripping”)

2.       Growth retardation: Transphyseal screw placement of transphyseal bridging (“screw and wires”)

Correction of these limb problems at an early age allows for the potential of normal loading of the hooves, joints and musculature and minimizing the predisposition of these horses in developing premature arthritis and lameness if left uncorrected.  Corrective osteotomy/ostectomy are much more invasive and expensive procedures that could be required if treatment is not recognized until after the closure of the growth plates.

Early recognition of the problem, regular veterinary re-evaluations for mild deformities and surgical correction of deformities prior to known physeal closure times all allow for a higher incidence of long term successful outcome.