Angular Limb Deviation in Foals

By Dr. Molly Bellefeuille

Hope everyone had a successful and plentiful foal crop born this year. The next time you watch your foals play in the pasture, look a little closer at their leg confirmation. Young foals commonly have crooked legs otherwise known as angular limb deviations. Standing directly in front or behind the foal, you should be able to draw a transecting imaginary straight line from the top of the leg to the ground. If you cannot draw a straight line, the angular limb deviation is located where the straight line breaks and turns. Angular limb deviations can be caused by a number of things both prenatal (prematurity, placentitis, soft tissue trauma/underdevelopment) and during development (unbalanced nutrition, excessive exercise, or trauma).  Most foals are born with some degree of deviation. However, most correct with age. This is due to laxity in tendons/muscles or underdevelopment of musculature and body mass.

There are two general terms used to describe angular limb deviation: Valgus referring to an outward deviation of the limb, and Varus referring to inward deviation of the limb. The angular limb deviation is also labeled depending upon what joint is affected. The most common deviation across all breeds is carpal valgus (outward deviation from the knee) Limb deviation may cause lameness, joint swelling, physitis, ligament laxity, excessive wearing of the hoof and in severe chronic cases joint collapse and development of arthritis.

To diagnoses and know the severity of angular limb deviation in a foal, radiographs of the affected leg are taken. Radiographs help to assess the location of the deviation, the degree of deviation from normal, the condition of the bones within the affected joint, the condition of the growth plates and help to evaluate the response to treatment over time.

Several treatment options are available for angular limb deviation in foals; treatments consist of non-surgical and surgical. The severity of the deviation and the age of the foal will determine what treatment is best. Treatments are best applied to younger foals before they hit their growth spurt (2-6months).  In older foals that have already completed rapid growth, the more severe surgical options are required. Non-surgical treatments consist of stall rest, splints/casts, corrective trimming or placement of glue on the shoe with inside or outside extensions. Surgical treatments consist of periosteal stripping (elevation of the periosteum on bone to accelerate growth), transphyseal bridging (placement of screws and wires to retard growth), transphyseal screws (placement of a screw through the growth plate to retard growth), or corrective osteotomy/ostectomy (removal of a wedge of bone if growth plates are closed or if rotational/long bone deviation is the problem).

Most foals respond well to treatment especially if treatment is applied prior to rapid growth, but all is dependent upon the degree of deviation, the joint and limb affected and if there is an underlying condition. Early evaluation by a veterinarian and radiographs of the affected leg will help you and your veterinarian develop a plan for correcting the deviation.  Straight legs are happy legs and help prevent arthritis development in performance horses. Happy straightening!