Deviation in Foal Legs

Foals' legs often look less than perfect when they are first born. It is fairly common for a foal to appear to be knock-kneed or bow-legged. Tendons that have not tightened enough to support the legs properly can cause the joints to appear seriously flawed. Some foals have two legs that appear to be turned in the same direction due to the way the foal was positioned while inside the womb.

Treatment

Just because most foals with crooked legs grow out of it; does not mean you should ignore the problems that you are seeing. If your foal appears to have a significant leg problem, then you need to have your veterinarian come out and evaluate him immediately. Some leg problems require early treatment for the foal to live a healthy, active life. A restricted or guided exercise and turnout regimen can help many foals with leg problems grow into useful, sound adults.

Normal Development of the Bones of the Forelimb

Since deformities are a result of abnormal bone growth and development, knowledge of the normal growth and development will be useful in understanding the development of deformities.

Growth in the carpal area occurs in three locations. First, the radius grows in length at the distal growth plate (physis). After the radius has grown to its adult size, the physis “closes” and no longer contributes to growth. However, rapid growth occurs up through 8 months of age. Second, the distal end of the radius enlarges at its margins. Third, the carpal bones enlarge in all directions during growth. Abnormalities in growth at any one or more of these locations can result in an angular limb deformity.

What is an angular limb deformity?

Angular limb deformities (ALD’s) are a relatively common set of conditions affecting foals, primarily during the first few months of life. The carpus, fetlock and hock are the most frequently affected joints and the condition is described by the direction in which the leg deviates from midline.

Causes

Many contributing factors for the development of ALD’s have been identified. Some genetic pre disposition may be present. Nutritional factors can play a part as well as maternal diseases that may affect the foal in utero such as: placentitis, colic and severe metabolic disease.Premature foals may also have incomplete ossification of these bones and early identification is important because the external appearance of the bones can be normal with the limb deformities developing later when the foal exercises. Pressure on these incompletely formed, weak bones may result in the development of an ALD.In addition, once the foal is on the ground, soft tissue trauma and laxity of the soft tissues surrounding the joints can also impact on the straightness of the leg.Older foals may develop limb deformities due to inappropriate feeding and the resultant dietary imbalance and disproportionate growth.

ManagementTreatment of ALD’s depends on the severity of the condition and the age of the foal. In the simplest of cases with only a mild deformity in a young animal, exercise restriction for a few weeks may be enough to correct the problem.Should the deformity be more marked, or the foal older, or should the deformity not have responded to restricted exercise alone, then a number of other options are available.

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Picture 1 – carpal valgus , the limb deviates outward from midline below the knee

Picture 2 – Carpal Varus, the limb deviates in towards midline below the knee

Picture 3 – Fetlock Varus , the right hind limb deviates towards midline below the fetlock

Picture 4 – Windswept foal , an abnormality in which limbs are slanted in one direction in one limb (valgus) and in the opposite direction (varus) in the other. In this foal there is a right forelimb carpal varus and a left forelimb carpal valgus

The age of the foal must be kept in mind when treating these conditions. The growth plates in different joints close at different times. Once they close then bone growth stops and so any correction required is then very difficult to achieve.

Treatment

Corrective farriery

Firstly the foot should be trimmed to balance the hoof wall. Nailed or glue-on extensions can then be applied to one wall whilst the other wall is often lowered by trimming.Regular assessment by the farrier, vet and stud team is essential to ensure this is aiding in correction of the deformity and to ensure that over-correction does not occur.

Shockwave therapy treatment

A useful non-invasive procedure that can be performed in the sedated foal to attempt to try and stimulate bone growth at the point of application. Shockwaves are high energy soundwaves that are produced by a projectile within the handheld unit. When the unit is applied to the foal’s skin they are transferred across the skin to the target tissue.

The energy transferred by the shockwave is thought to cause an inflammation –like response and recruit new blood vessels and bone-building cells (osteoblasts) to the area.A typical course would consist of 3 treatments at 2 weekly intervals but is dependent upon progress.

SurgeryPeriosteal strip – this involves cutting into the periosteum (bone lining) and releasing the tension at the level of the growth plate, therefore accelerating growth on the shorter (stripped) side.Transphyseal Bridging – a screw or wire with screws can be placed across the growth plate to slow growth on the long side. The implants can then be removed one the desired growth retardation has been achieved.PrognosisThe prognosis for ALD’s is generally good if the deformity is identified and quantified early and the appropriate management instituted within the window of opportunity for that particular joint. In most instances, conservative treatment alone is generally most successful.